Basically the hardest part of this fight is the pull. In a nutshell, the 4 adds will pounce straight on top of the first person to have aggro, killing them instantly. Our solution was to hide out of line of sight and have a Shaman drop a totem on her way while she is coming, Our deathknights put down D+D on the corner, so that the adds had a small amount of aggro and don't just hit the healers. Then misdirects were put on to ensure they weren't all attacking the same tank. Timing on this is all-important, basically misdirecting as soon as they're in LoS. It's VERY important to have cooldowns up on the tanks as they do this; pain suppression, guardian spirit, and so forth. Otherwise the tanks will die in seconds. Additionally, it helps to hit heroism as soon as the adds arrive, this helps with the healing, and you want to make the adds dead as soon as possible.
While killing the adds, the boss will begin fearing. Fear ward on an add tank, otherwise the adds can go a bit crazy. Tremor totems too. The first wave of small cats (these can be AoEd) and the big cat will then arrive. The big cat mostly runs around randomly like crazy. You can heal through it, even against cloth-wearing classes although sometimes you'll get unlucky and it'll go for the same healer time and again. You can kill the big cat, but it'll leave a void zone where it dies, and then come back after 30 seconds or so. Each time it dies it gets weaker, it has 9 lives in total. The damage is healable anyway so you don't need to kill it.
Like this all we had to put up with is fear and getting back to the original position and the low raid damage of the Feral Defender dashing from player to player. The interrupts were an annoyance we had to put up with but it was still easier for us this way, by far.
RECAP: 1.) Keep the MT and the OT topped off (beacon of light is very helpful for both of them) 2.) Run out of the big, bad, Void zones. 3.) DONT Spread out, and watch the sonic screech. 4.) Rinse and repeat.