More info on this fight. (mostly copied from hunter post on Wow.com)
Avoid getting slime sprayed. One way to gauge your performance on this fight is to see how much
Slime Spray damage you took. You want that number to be zero.
Be aware of where the kiter is at all times. When you get the Mutated Infection you don't want to waste any time trying to figure out where your kiter is.
When you get Mutating Infection, MOVE toward the kiter. Your goal here is to get rid of your ooze as quickly as possible and return to the center.
Remember to continue dps on Rotface while you're dealing with your infection and ooze. (When possible)
Kiting:Do not ever let it get too close to you. The Big Ooze is perfectly capable of two-shotting you.
Do not get too far away. Since you're going in circles, the farther you get the more "corners" the Big Ooze can cut, and it can and will cut through the center of the room, hitting the raid with its aura.
You will have to kite through the ooze flooded portions of the room at times. Do not try to switch directions. Your healers can deal with it.