As far as I know healing touch is only capped by Eirin's capability to heal. The healer subclass's heal did get nerfed by ~40% between the plus disk but she should still be able to at least triple Tenshi's HP with some buffs behind her.
SHK and DTH strength don't matter as far as I know (since they're both instantaneous). I have no idea why it's labelled as 10000 for Cat's Walk.
No idea about exact HVY/SIL, though I'm pretty sure it's way more than 8%.
Ah, thanks, that's good to know. Are the current stats of 60% ATK + 60% MAG on the Wiki page for Healer's Prayer of Recovery the Plus Disk stats then? If so, that seems good enough, especially if it can overheal to that kind of extent. Unless that has more to do with how low Tenshi's max HP is, but either way, it sounds like Eirin would definitely be very helpful to have. The SHK/DTH thing I kinda figured, but wanted to be 100% sure on.
Went back to double check about the SIL thing I read, this is the stat debuff mentioned.
Mystia... I always thought the only truly useful thing she brought to the table was Extra Attack, and somewhat the fact that she gets a 120% chance SIL skill (although SIL is mostly only useful to trigger her stat boost passive and stuff like Final Attack; 5% lower mag/mnd is pretty minor.
It seems weak, but at the same time, the 5% stat debuff that PSN inflicts mentioned in the same post is left unmentioned in the JP wiki, either through omission or because it's unknown, so I can't exactly trust it blindly either. I guess just messing around with HVY and SIL and seeing what kind of numbers result from it would be a good idea, just to be sure.
*Snipped for length*
Sounds like I should skip Rin and Satori then. If Rin isn't worth using for SHK alone, and Maribel does the job fine with support, then another character performing a different role would be more useful. I think I also place too much value on Satori's Trauma Recollection, besides that she wouldn't be adding anything to the team due to only having spell cards other characters use, which isn't bad, but probably would be better to replace her with someone else. Might apply to Rinnosuke as well, in that he may not be justifiable compared to other characters.
Hina does look like a really strong debuffer, but if I'm going to use Reisen, it seems a little redundant to also use Hina, so I'm not sure if she'd be worth using over another character that offers something different. Reisen seems really solid and versatile, especially with Intense Vertigo, so between the two, Reisen seems like the more generally useful.
Based on what's been said about Yuyuko, sounds like I should skip considering her if the ATB reduction isn't as useful as I had initially thought. Something that would be more generally useful and reliable would be preferable then.
Renko seems really difficult to use in combination with Eirin, since Charge would reduce the overheals, so I'm not sure about it. I guess it would be fine if no character is overhealed, but it seems a little complicated nonetheless. Something more versatile may be more useful.
So I should focus more on Last Judgment with Eiki when she's out, and probably keep Keine then. Keine would help make it easier to keep ATK/MAG buffs up without relying on Iku, so there's definitely a useful, distinct role she can play in that regard. Keine's defensive skills look really interesting and useful (especially History Accumulation), it looks like I can expect her to be able to hold her own defensively and as a support character.
I think I'll add Aya into the team then, the speed-oriented support would certainly be valuable. One thing in particular I'm thinking about is that, post-Awakening, for bosses that Tenshi can strike weaknesses on to trigger Keypoints of Spirit, it would probably be ideal to max out her counters as quickly as possible, especially if it's necessary to use a weak subclass spell. Aya would be very helpful for this, in addition to all the general uses speed buffs and extra turns can get. The poor defenses are a bit of a concern, but it's not like any other character can play quite the same role that Aya can.
With the empty slots and the ATB reduction niches being narrowed out, Cirno looks like she'd definitely be more useful than I initially anticipated. Going to have to more seriously consider adding her then, she might be worth the party slot. My main concern is how weak her speed debuffs are on targets immune to them even with her irresistable debuffs. 1/5th of 44% on Icicle Fall is only 8.8% (I assume it's rounded down to 8%?). But stacking that might actually make a big difference, especially if that's the only way to affect the target's ATB.
Kogasa's usefulness seems really difficult to measure, but the full team heal against TRR'd targets is very strong. If nothing else, she's fairly unique, so I'll have to keep her in mind.
Think I'll skip on Sanae then. The other thing that really stood out was that she can buff SPI damage by 30%, and Tenshi's Sword of Hisou is quite strong and SPI element, but I don't think that's quite enough to be worth using either.
Tenshi's Keystone Formation skill looks really valuable pre-Awakening, but post-Awakening, I think it would be better for her to spend her turns either building up Keypoints of Spirit counters on bosses with weaknesses she can hit, or just attacking in general. Since switching rapidly would remove counters and reduce her offensive buffs, it would make taking advantage of her offensive capabilities more difficult. Though, making use of Keystone Formation looks to be the most useful thing she can do prior to Awakening, generally speaking.
Hmm, Enhancer looks like a good subclass for Iku, yeah. With maxed out Enhanced Buffing, that would be 84% ATK/MAG on a maxed out Thundercloud Stickleback, and 48% DEF/MND for An Ounce of Prevention (although, the DEF/MND buffs seems small compared to what Reimu and Yukari can do with their Barrier spell cards). I'm going to have to play around with her and see how durable she is with Tenshi's presence to be able to determine whether she can afford some MAG investment or not. Elekiter Dragon Palace's DEF debuff alone makes it pretty nice looking for when Iku doesn't need to buff, being able to do good damage with it would be very nice. If protecting against the drawback of Whiskers of the Dragon God is unviable for most of the party members, then Aya will be able to perform more of a role than I initially thought, which is good.
Regarding the recommendations, Kaguya's Awakening skill that enables allies to ignore 25% of a target's defense stat looked really interesting, but she seems squishy and doesn't really offer anything else besides personal damage output. There is the synergy skill, but Reisen can do that too, and while it'd be strongest with Kaguya too, I don't think that's enough to be worth the character slot.
Next to Kogasa, Mokou came off as the most useful user of Sheer Force (assuming Awakening though), since she can apply ATK/MAG debuffs. But Reisen can apply debuffs to all stats at a stronger magnitude, along with all the other things she can do, and the rest of Mokou's skills are for herself (besides Blazing), and the way I want to use Keine wouldn't be able to take advantage of the synergy skill, since Keine gets ATK/MAG buffs.
For bulky damage output, I think I'd like to focus more on characters that are capable of dealing in support as well. Of the five mentioned, Suika came off as the most interesting, since she could apply PAR whenever she took a turn and had some decent debuffing attacks (although probably Suika would be doing direct attacks instead). Fog Labyrinth boosting EVA by 20% would also be a uniquely useful support skill, if it weren't for Tenshi having an EVA of 1. It might be helpful for the dodgier characters like Aya though. The rest seem more straightforward in that they mostly support themselves, which I think isn't too helpful for this. Though it would be important if, regardless of preparations taken, the damage output just isn't good enough to beat bosses that strengthen themselves over time or use overkill defense ignoring attacks. I think characters like Iku, Eiki, and Miko might be able to handle this, but if they can't, then a more straightforward damage dealer might be important after all.
I think I'll put Reimu in one of the empty slots taken out so far, she looks really useful. One thing I'm thinking of doing with Reimu in is taking Yukari out, since IN Quadruple Barrier becomes a little redundant, and I think I've overestimated how useful Border of Power and Magic can be. It might be better to just split Tenshi's defenses and not worry about stacking as much ATK as possible. This would allow the most stable defense and allow more versatility. I may be overlooking how useful Yukari's Spiriting Away can be though. It doesn't seem like the kind of spell card you can just use without a goal built around it, and I don't see it being especially useful for this party structure outside of attempting to SHK lock a boss or something (Yukari + Maribel + Aya I guess?). Rumia also looks interesting, her Awakening skill that grants debuffs to Moonlight Ray and Dark Side of the Moon sounds like it has a lot of potential, but without knowing the strength and application rates of the effects, it's hard to ascertain the value properly, so I don't know if she'd be a good fit or not.
Lastly, Nitori and Momiji...I don't think they really offer anything new in particular, besides Nitori's Super Scope 3D being much more damaging than what any of the other characters are capable of. Since the synergy skill only works on the front, and I'd prefer to have Tenshi and Iku in the front as much as possible, that leaves only 1 other slot if Aya's up. If I were to take advantage of the skill, having just 1 of the other members would probably be best. Of the three other characters in the synergy, Hina seems like the most useful. Having Aya grant Hina extra turns to rapidly debuff a target doesn't seem like a bad idea actually, provided that it doesn't have 100 in anything (otherwise Reisen would be more useful)...which sounds really unlikely, actually...
Yuyuko looked really exciting on paper, but in practice I found her a lot less exciting. Her lack of damage increase passives or things along those lines, along with her high cost library, actually makes her damage a lot lower than I thought it would be... even with her seemingly powerful moveset. Every boss I think "great, now to bring Yuyuko out and- oh wow she's actually not very useful in this fight...". As for Iku, she's actually really effective in that normal attack build, imo, and the heavy amount of mnd piercing is sweet (whether normal attacks or not- but she easily gets 90%+ ignore on normals). Since you want her synergy with Tenshi you might want a tankier Iku built for support though? Generally I think support-Iku is actually not worth the awkwardness in LoT2 with all the other options you have for buffing instead, but if you want the Tenshi synergy, it's on the table.
Kogasa is a great SHK option as guardian when you need that for a boss (it's surprising high SHK proc, and then sheer force...) , to help out "but I can't TRR this well" problems- overall she's a little awkward until she Awakens. I think she's got amazing potential as a party regen tank after that, but I can only say so much without real field testing for that, and you can only awaken a few characters until mega-endgame.
By the sounds of it, instead of having Iku as support with Thundercloud Stickleback, it would be better to have her play as a bulky attacker and have a different character like Keine handle ATK/MAG buffing, except for characters that can or have to resist the PAR effect. Tenshi's State of Enlightenment has a 96% PAR rate at level 5, so that probably warrants PAR resistant equipment, at least for post-Awakening. Actually, having Iku as a bulky attacker sounds like a better idea in general to be honest, and certainly more interesting than pure support.
Shield Bash + Sheer Force does look like it has a lot of potential for SHK shenanigans, that seems to be the most useful thing for status that Sheer Force brings to the table. Between that and the TRR stuff Kogasa brings, she looks like she could be really interesting, plus all the skills that benefit her personally. Astonishing Ghost Umbrella in particular is amazing defensively, with that -40% damage reduction against TRR'd enemies.
When I first read the skill's effect I misunderstood it to work on everyone, not just Kogasa.--
So looking over everything, from the original team I had in mind,
Rinnosuke / Keine / Rin / Satori
Eirin / Reisen / Yukari / Eiki
Tenshi / Iku / Maribel / Miko
Remove Rin, Rinnosuke, Satori, and Yukari (-4)
Add Reimu and Aya (+2)
Then from there, the most interesting characters so far are
Cirno (SPD debuffs)
Kogasa (TRR, Sheer Force, HP regen every turn)
Suika (60% PAR attempt every turn, passive EVA buff)
Rumia (post-Awakening status and debuffs, party-wide heal)
Of those...Cirno and Kogasa seem like they might be most useful. Besides the option of Shield Bash backed by Sheer Force, if Kogasa can TRR something post-Awakening, that's a huge HP regen every turn, and Cirno provides a way to slow down bosses that are immune to SHK, probably better for this than Yuyuko is. These are more specialized uses, but I think general use has already been accounted for well enough.
That's what I'm currently thinking of, anyway, might need to make further revisions. Thanks for all the input so far, it's been very helpful!