We spent about 90 minutes putting up with random bugs before we killed this fight so I figured I'd make a thread to share what happened to us and how we fixed it in case someone else experiences the same thing. I didn't find another thread like this, but sorry if I'm duplicating anything. Feel free to share your experience here as well (this fight seems quite glitchy).
Phase 2 not starting
This one is simple, just don't switch platforms until after Deathwing moves his face. If you try to jump onto the phase 2 platform prematurely then phase 2 never triggers, just stay at your 4th platform until he moves and only then go after him.
Corruption Tentacle one shotting people
This happened to us quite a bit, it would just randomly turn and 1 shot melee even though they were nowhere near aggro. We fixed it simply by never taunting, we used only 1 tank for phase 1. However this might have been simply an Omen bug, I'm not 100% sure. With the recent threat changes to tanks though... I kinda doubt it. Our tank had a huge threat lead when it happened and it 1 shot ALL melee DPS. I think threat on the tentacle just bugs out after a taunt.
Corruption Tentacle never spawns
Just went for an entire platform and it never spawned. *shrug* all good, just saves healers some mana. The Elementium Bolt never came either, beneficial bug.
People falling in water during jump
Fuck if I know... good luck here. I have no idea what causes it or how to fix it.