I hate this buggy instance.

I pretty much have it on farm, usually no deaths, unless the mounted phase produces a bug.

Apparently, if you kill the last mounted champion while another one is jumping onto a horse, it'll bug, you/they will dismount, except for the guy that just mounted. He'll stay mounted, and start trampling your guys.
Go outside, reset.

Yesterday, after killing the 3 champions on foot (luckily, I had hunter/mage/healer, no warrior or rogue), I'm running to the center where the chest has already spawned, and the mage comes back to life and starts casting on one of my shamans. I reacted too slowly and he killed it.
I grabbed the mage, tanked him and got him down.. at which point he MOUNTS UP!
He then proceeds to trample and kill two of my guys before I can run out of the instance.

All this time, the chest is already up, I quickly looted it while running out of the instance in case it bugged too somehow.

Luckily, when I went back inside, mage was gone and I could start boss 2.

I hate this instance.