TRR killed Zakuun on Heroic after about an hour of progression Sunday with a raid size of 15 (? 14?). The fight mechanics are largely the same as on normal and just hurt more with a few major differences:
* When the tank comes out of the jumping realm, they will explode into waves similar to how people with the seed debuff in P2 will explode. Tanks can see raid flares (floor markers) in the other realm, so we found placing a flare where the tank should come out helpful -- players in the real world just avoided this area of the room.
* The debuff from blocking a pillar from spawning lasted longer, requiring multiple teams to be assigned to this job instead of just 1-2 people handling it every time. At 15 people you'll want two 2-person teams with a few more people familiar with the mechanic in case more spawned. (TRR was seeing 4 pillars in P1 right after the first Disarm/P2)
* Corrupted healing-absorb debuff goes out on more people per raid size. At 15 we were getting 3 each cast. Healers found it helpful to target heal specific players. We cleared debuffs alphabetically.
* It seemed like there were more pillars to block and P2 debuffs going out than happens on normal at the same raid size. At 15 this usually left us with 4-5 people available to use their bodies to block waves from hitting pillars, so everyone needs to be on the ball with this.\
* We found placing raid markers for seed/debuffs for P2 in P1 once we had a good feeling about where pillars were helpful. You do not want 2 people with seeds going to the same corner of the room or they will kill each other.
* TRR's healers were doing 70k-93k hps, but I suspect these numbers are inflated due to having a high number of explosions, and healing needs are probably not this high if mechanics are handled better. The healing stress points in this fight felt as though they mostly occurred in P2 and to a larger extent P3.
Overall, Zakuun is not that hard though, and we killed him after Iskar and before Socrethar.