Sometimes he just wouldn't keep it up, I don't know why. But I saved cooldowns for 2nd dude (killed the small one first) to get him down ASAP. When my pet was about to explode while on Steelbreaker, I dismissed and resummoned it (it heals Steelbreaker, so remember Widow Venom, but you can use the same pet and it won't be dead and won't have the debuff). Then you get the crazy buff yourself and the pet does too after you Feign, and he dies super quick. I can highlight the VoD on twitch later when I'm done streaming.
Edit: Dat soft enrage on Ascendance Council ... I got him on 8% once. I was using 5 Spirits Beasts for the extra healing in phase 1 because Heart of Ice just wrecks me, but I'm trying with a Core Hound now for the Bloodlust. I can't find any information about an enrage other than the damage in phase 3 acting as a soft enrage, so by prolonging phase 2 I could get a lust both in phase 1 and phase 3, which hopefully is enough to bring the bastard down.
3% attempt... It's SO much fun waiting in phase 2 for ~9 minutes for lust debuff to go away.
Double KO! I died, but so did Ascendance Council!
Cho'gall down as well, so BoT normal is cleared. Tried to swap to heroic, but you still have to kill Cho'gall on heroic to unlock Sinestra, it seems
Lord Rhyolith down on 10 normal.