Vulak has its own lockout, if one person in raid has that lockout does that not prevent vulak to spawn? Is there not also an npc that checks for lords/ladies are up, if none are it spawns vulak? Why cant that be on a lock out also?
+1 for picks in Temple of Veeshan; Zone overcrowding is what pickzones are for, why exclude this one?
As far as I understand it, because of the unique way that he spawns, the lockout actually doesn't matter. If there's a lord or lady up in the dz, and you kill them all, Vulak will spawn. With loot. And the check is on the Lords/Ladies death, not just that they are not up. If you go into ToV with all Lords and Ladies on lockout, Vulak will not be up whether you have him on lockout or not. People have made the mistake of "saving" Vulak for another night, after clearing all the Lords and Ladies. When you come back, there is absolutely no way to trigger him if there isn't a Lord or Lady up in the fresh dz.
Thylex of Veeshan is what checks for the lords/ladies dying to spawn vulak, having vulak on lockout prevents thylex from spawning.