TheBlackMarvel
Member
Here's what worked for me in phase 2: Keep your distance and keep dodging back to avoid the swipes. The arena is shaped like a rectangle, so make him chase you up one edge, and then turn to the other edge and keep going around. The only time you can safely attack is when he decides to spew his lava breath, and that's when you should quickly strafe/dodge over to his right (your left) and unleash a single charged R2 attack. Just keep that up, and you should be able to take him down with minimal risk.
Oh, and try to equip some HP runes so he can't one shot you, that way you're allowed to make some mistakes while keeping your distance. Just don't get greedy and stick to the plan.
I don't think there's a legit way to cheese him, but he's very susceptible to parries (in both forms) so you can try learning the timing for those.
Interestingly enough, I gave up charge r2ing him when he did the lava because I always got vacuumed in and the lava annihilated me. Will try again.