ok, managed to down Attumen and baron Gedon today.
I can't seem to get past Garr though. Tried nuking him down, but then adds killed me after MI. Tried AoE'ing down the adds while using MI, but that didn't work either as I couldn't down them in time.
Anyone has an idea on how to tackle this one as frost?
[edit]
I managed to down Garr as well.
Tacts:
Put up Mana shield, slow fall, mage ward and ice barrier and refresh them as soon as they run out due to damage or the dispel aura.
Put pet on Garr. Pop MI and IV. Start killing the firesworn with single target dps. Piercing chill, CoC and frost armour will allow for quite a few FoF or BF procs to help to get them down fast. After I think 4 or 5, MI ran out so I tanked the firesworn while my pet was still on Garr. After I killed all the adds, I healed with evocation and started attacking Garr.
I popped invis as soon as I took agro of my pet, but regained before he went down. So I tanked about 40-50% of him which wasn't that hard considering he hits quite soft while mana shield and ice barrier helped negating the damage.