Also keep in mind the tips from former post, e.g., my first post about healing strategy for this fight. As I already pointed out, imho, what matters most is having a proper plan for this fight. It's just all about synergy between classes and organizing the different phases, e.g., fast re-stacking after the kite phase, not having people with debuffs out of range, arranging cooldowns.
We killed him the last two times with only one tank, our first kill was with two tanks - just to give you a hint to alternative strategies.
Just try to find what works best for you.
PS: Just plugged you into AskMrRobot and optimized your gear and gems for a haste build. You could reach the 15k haste with reforging completely into haste and changing all your gems to pure haste gems. Just fyi.