I'm at 5500HP in PT. Titan mountain busters for 3500+dmg if I dont have cooldowns popped, it's also followed up with an 1k dmg auto attack. I get my Curtana +1 today so I think i'll push 5600+ soon.
Edit: After completing turn 1 of the coil last night there is no doubt in my mind that stacking as much VIT as possible is the way to go. That snake hits HARD. I went into the fight with 5700+HP and needed every single hit point.