How far do you plan on taking that sub-par party?
Unless I get completely stumped at a boss and have to face unrealistic amounts of grinding if I want to get past it, I'd be going for Final Boss. No Plus-Disk stuff though (most likely not, at least)
And actually, most of my squishy characters have an at least decent MND stat. Youmu/Cirno/
are the ones with bad MND, but I might go for HP bonus on Cirno (is her damage enough late-game for ATK levels to be worth it?) and Youmu has great HP so she takes a hit from MAG, and the third, well... blah, at least she has good SPD and a self-buff on all stats.
But yeah, I'm wondering how many (if any) MND levels I should be putting on my tanking characters. They NEED to be able to take major physical hits and are not ideal tanks, thankfully they both have 100~ level up rate and a MND growth of 7, which means their MND isn't bad at all.
Oh, and I'm not sure what to do with Iku. I'll probably mostly use her for buffing my (mostly squishy) damage dealers, which means she'll probably end up in 3rd (possibly 2nd) place sometimes. Her attacking ability is okay, but I need her to survive for buffing, so I'm wondering if I should boost MND (this would give me a good 2nd slot tank for MAG-only bosses like 16F and most of the final boss) or boost her less-great DEF stat so she can take all kinds of hits well.
Then again, with my low amount of damage dealers I can only hope Cirno helps enough with random battles to make up for my boss-killing-oriented party. Giving Iku MAG might be helpful for that... but... gah.
Maybe giving her MND for a MAG tanker against certain bosses would be best. 3rd doesn't get hit by physical attacks too often anyway, and she shouldn't usually get 0hkoed by them.
Also, sub-par is also meaning basically "all the characters most people agree to not be very good and don't use". Of which I'm using almost all of them save maybe 2 or 3, all that I can while still having a possibility of winning without mass grind.