Unable to land Blood of Saryrn with it when Malosinia is on, so my hunch is poison immune besides unresistables (like Tash, which has poison counters). Disease dots and magic spells landed just fine.
Those are really dangerous, even for high Levels if they dont know what they are doing. They have a disease based AE Nuke that usually hits in 3 Waves, and hits VERY HARD for a mob of that level.
If you not familiar with them i recommend sending in only the Maintank and have everyone else stay outta range of the AE - let him build some agro and than nuke him down, doesnt have many HPs.
Really recommended that everyone tries to max diesease/poison resists when moving deeper into Cazic, gettin one of those AE Casters as Add can wipe your whole party quick :P
these cast aoe rain is a 50+ shaman spells is poison based so buff that .. from a 50+ shaman lol The aoe slow is anoying but just nuke them like super fast they try to heal its only like a 300 hps heal though.
We had a full group avg level 54 and it still took down 3 of us. Damn rain spells are tough to resist. I had MR of 127 and all other resists around 70. Watch that HP bar and get out of the rain.
I believe the aoe slow/dot is Bane of Thule. Seems to cast it once every 10 or so ticks. If you have several mobs mezzed, save these for last and take out the warrior style mobs first.