Yikkan Izu

Despite what some people are claiming, this fight does not appear to be bugged. It does, however, appear to have changed slightly from MoP.

In WoD, Yikkan will enrage when he gets 4 stacks of his buff, not 5. He also appears to summon birds much slower then the 8-second cycle he did in MoP - it seems to be closer to 12-15 seconds. When enraged, Yikkan will start summoning huge swarms of birds very quickly, which is why many of the commentators are being overwhelmed by adds.

Instead of making sure all birds are dead before he summons in his next pack, you have to kill 1 bird, wait 2 seconds, then AoE down the other 3 before the next flock spawns in. This will prevent him from enraging, and allow you to kill him normally.

As an aside, the turrets from the Workshop are incredible in this fight - they can add 7-10k more DPS, and they always shoot at the thing you're targeting. You don't have to worry about them killing the birds accidentally.

the idea is to not kill 5 birds within 4 seconds, or he'll enrage, he spawns them in lots of 4, every 8 seconds.

At the start of the fight you’ll see 4 birds swarming around him. Make sure to AoE these birds before the next pack spawns. Killing more then 4 birds at the same time makes Yikkan enrage so just keep on aoeing all the birds. Alternatively you could just make him enrage and kite him around, but it’s not required.

http://www.youtube.com/watch?v=hLa72xgFevw&t=10m53s