Mastered Odin. Got kinda lucky. I did in fact have some FF13 synergy in the form of a dagger, so I tried Come At Me Bro not really expecting it to work, because it really neuters my damage otherwise. That said, his big attack (Heaven Strike?) isn't Reta-able, but does respect Taunt, so fortunately Gilgamesh is pretty tanky. His other big attack, 4x Strike, IS reta-able, though, and went off twice, netting me a cool 3500*8 damage, which is probably about as much as he would have done with Banish Raid over the course of the fight, so hey.
Party ended up being
Ramza (Full Break, Power Breakdown)
Zack (Indoor Spell, Drain Strike)
Agrias (Vanish Raid, Protectga)
Gilgamesh (Come At, Me Bro)
Aeris (Shellga, Curaja)
Scream RW
Now, what would have been smarter, and would have been give Agrias the dagger, put Taunt on her, and put Drain Strike on her, since that would have given me enough synergy to heal from Heaven Strike. I'd still need protectga, but I now have two protectga relics, so I could have put my Attack Ribbon on Gilgamesh and combined that with Mako Might. Well, I probably would have swapped Gilgamesh for Faris, actually, so I could have access to more Breakdowns. But regardless, it worked this way so whatever.
Re: Reraise. I'm aware that I have it, and I'm aware that it cheeses out doom, but... honestly Reraise is basically false hope if your whole party gets offed in higher level content. Don't get me wrong, having reraise is strictly better than not having reraise, but consider this. When you revive, you revive with 25% HP AND ALL buffs cancelled. So, best case scenario, only one person dies and you're frantically trying to get your mitigation back up and heal back up to a survivable HP before they get RNG-offed, and you lose some turns you could be using to do other things. Worst case scenario, which happened every time I tried to just YOLT through Doom, is everyone dies at the same time and the boss uses an unmitigated MT attack next turn that wipes you out regardless.
Reraise gets much more utility from being a safety net in case a single person dies. In lower level content it could be used to just cheese past doom, and in higher level content it can be used to cheese past party-killing moves that also cause the boss to Suicide (thinking Demon Wall 12 here), but it's not even that good as a last line of defense for full party survivability.