Mostly refering pre-nerf boss. Post-nerf, none of these bosses are really that hard anymore.
Stonecore
1. Corborus -- People moving too slowly to avoid the dive, and lack of good range AOE to kill the crystal fast enough. On the first 2 weeks of Cata, it is not uncommon to swap through 8-9 players before finally killing it (or sometime never)
2. Orzuk -- I called it a Tank graduation fight. Our guild still uses this encounter to trial our newly recruit tank -- good for testing their footwork.
3. High Priest Azil -- This is usually a very easy fight, except when you have a weird group with no good interrupt on the Life Grip. The grip will hold the tank up the air for a long period of time, and then ending the grip with a throw that does large chunk of damage.
Grim Batol
1. General Umbrise -- This is hard mostly because bunch of people dying from Blitz
2. Dragha Shadowburner - Average PUG just can't handle the fire elemental and dodge the shadow breathe.
3. Erudax -- This can be hard when the group doesn't have sufficient DPS to bring down the adds [sometime due to weird group setup where no one can slow down the add]
Vortex Pinacle
1. Altairus - Pre-nerf, the wind can chain bounce you everywhere. Healers that can''t adjust their position to get haste buff have great difficult keeping the group up too.
Hmm, can't really count to 10 difficult one lol
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