Honestly, I think this Heroic sucks. It really, REALLY depends on your roster. Good side? There are plenty of viable tactics, and the roster requirement isn't EXACT. It's just that there are some ridiculously good Hime for this fight, such as Dian or Shamash. But other valuables can be Beelzebub (taking 1000/t is pretty nice for the first fight, just DON'T DIE TO IT which can happen!), or SRs like turtling-GOD Culyune, Konohana-Sakuya and Buer can be used well.
But yeah, having to do two completely different fights WHILE ALSO bringing full debuffs is really rough. EVEN MORE SO in an element like Fire, which sucks total ass in Grids right now if you haven't invested in Fire Hime weapons. If this event had come after Phaleg+ fight which also buffs Phaleg Staves (something that hasn't been discussed on these forums because these forums are deaaaad), then the fight would've had far, far more leeway to it. Now it's... pretty much a crapshoot about what kinda roster you have.
Personally? I just looked at my Fire roster, raised an eyebrow since apparently I have found three Fire Limiteds from Limited SSR Guaranteed gachas, slammed those (Shamash-Tish-Artemis) into my team with Awakened Mars and just one-shot the fight with my utter garbage Grid. Pay2win, motherfuckers. I haven't even noticed getting those since my Fire Grid is so awful using a Fire team isn't worth even considering, but I guess once Phaleg Staves are here my Fire will be decent a force to be reckoned with. I just wish that Labyrinth events wouldn't have been thrown into the trash, since a Labyrinth Sword Grid would've been a decent alternative to Phaleg Staff Grid but... sigh. I guess Phaleg+ grind it is, then.