Well, *knuckles cracking*, time to try to beat me a final boss. It's go time! :V
EDIT: Well. At Reimu 128, I beat it on my first try. That's not to say it was easy, however. I rocked the first part of the fight pretty well, keeping significant buffs up thanks to Ran/Reimu mitigating any threats while I switched nukers in and out to keep up the damage. Suwako paralyzed the PHYS summon for the majority of the battle, and I relied on Alice's MAG debuff to keep the MAG summon under wraps. All went well, but the PHYS summon went down first. Managed to kill the MAG summon quickly afterwards, but the Support summon got of a DEF/MND buff, followed immediately by the SPD buff, right before I killed it, causing the boss to seque to Overflowing Natural Power already buffed.
Ouch.
From there, it still seemed good. I'd saved 18F's buff to Nuke her down really hard and fast. But right after I spent the buff...she Djinn Stormed. That plan ruined. At that point I was only down one person I think (Flandre got sniped the instant she hit the board, more or less, made a mistake there), and it was a grind to the finish. Couldn't really nuke her down before she'd kill me, so I was forced to cross my fingers and pray she didn't overbuff while I tried to whittle away at her, rebuilding my SP and defenses. Suwako was the MVP here, as her REC rate combined with her high dmg and fairly cheap nuke allowed her to do the vast majority of the dmg in the final form. To that end, I was incredibly cautious with her. Patchy was useless with her pathetic REC rate, Youmu got debuffed out the wazoo and was only useful for switching (-50% to everything, basically) but Reimu managed to keep recovering JUST ENOUGH sp along with Ran to keep everyone alive. In the end, Suwako finished her as my party basically was finally spent.
Ironically enough, I think that's how i beat all of the later on bosses. Came in for a run, had some bad luck, and just ground out the ending out of an incredibly bad scenario to win, while generally being underleveled for the battle.
All in all, it was an incredibly intense battle, which equals fun for me.

Now it's time to consider moving on to some of the Postgame while I prepare for the start of the school semester...