So.. I tried turn 1, I was the off tank, the main tank always forgot to turn on Shield of Oath and also Fight or Flight before pulling Rayquaza :S
Anyway, when the boss splits are the DPS supposed to continue feeding for the stacks? I was off tanking 5+ stacks and died most of the time. People gave up in the end, I didn't do nothing wrong. I hope.
Hey, even the best tanks has some lapsus regarding Shield! (like me)
I barely had any party that keep feeding the snakes. Im sure that's the intended way, but if your DPS don't suck by 4 stacks both snakes should be closer to death.
The only reason you may need to feed him after being split is because he had 1 stack when he did.
That said, "dying" is not such an anormal thing. At that point the surviving tanks kites the fusioned snake.
Also try to wait until 3 stacks to start using your CD, but 5+ stacks means basically death, your team DPS sucks. Period. Not your fault.