Team: Mitra, Mediana, Philop, Naila
This took me quite a few retries, but I wanted to show that it can be cleared without having a 4* or 5* Unique Weapon (UW). My Mitra only has a 1* UW, and Naila has a 2* UW (and is only T3, lol). I believe Naila can be replaced by a T5 Gau, but he needs to have a DPS build since Mitra won't do enough damage on his own with a 1* UW (maybe with a 2*).
My other gear, other than the stuff on Philop, is pretty decent, but nothing too crazy other than the Beast of Chaos gear on Mitra. It's shown in the video.
Anyways, as you'll see in the video, I just barely cleared it, but that happens. There's a lot of randomness involved here, since Naila's passive (her forth skill) needs to work enough times to knock Manticore down. There were also some lucky misses in there. Knocking it down increases the damage you do to it and messes up its attack pattern so that it'll skip the scorpion summoning (which will likely cause a fail if it gets that off even once).
The main things to do on this floor is mess up it's attack pattern so he skips the scorpion summoning and have a way to deal with his claw swipe. That claw swipe will likely wipe out your team, so you either need to be immune to the damage it does (like with Mediana's first skill), or knock it down before it uses it. The rest of the attacks aren't too bad. The fire breath dispels, so save your buffs until after that attack is over with, and the poison breath can petrify you (which is annoying if you don't have a cleanser) but neither are all that bad.
The music is from the Resident Evil 5 OST: Wind of Madness.