Some other things we do to help this fight out.
-We save lust for a red/black/yellow phase because it is the hardest
-On Red/Black/Yellow phases we have dps hold off on blowing their AOE cooldowns until the second wave of adds has spawned. They still cleave/aoe through the first wave but any big aoe cooldown, ie cumbustion/bladestorm/etc, is held off until the second wave spawns. It seems to help get the adds down quicker. Additionally we hold our dps back a few second after the next wave of slimes spawns to finish off or get close to finish off the last of the black spawns. Then ALL dps heads out to slimes to kill the target.
-On one of our phases, I think its black/purple/green/blue (I think) we actually kill black instead of green. We found that dealing with purple and the minimal green damage was easier to heal through than purple plus the add damage.
-We 1 tank (Blood DK)/2 heal it, Holy Pally (me), and disc priest.
-During purple phase we each take a group, ie I take group 1 and disc priest takes group 2 so we dont over lap heals on accident and blow someone up. Very rarely does it seem like someone takes more than maybe 3 stacks before they reset in our group though. Something for your holy pally if you have one is that beacon does not cause a stack during purple, so all xfers to the tank via beacon are not going to cause stacks and I believe WoG also doesnt add a stack. Additionally if you happen to pick up a disc priest anytime have them unglyph their PW:S and it will no longer cause a stack during purple phase.