At lvl90 prot warrior you can solo this:
- Engage boss, fight phase1 as usual
- just when phase 2 starts (with the chains) jump off the platform behind the small building (where the stairs start at the bottom), pop some defensive cooldown, gather the spirits lurking around there and then aoe anything
You don't need to finish the boss after getting the achievment.
At lvl90 you can solo this (if you have some selfheal, defensive cooldowns):
- Engage Boss and bring him to about 20%, ignore all adds, the small ones despawn at some time anyway ( although the boss hass 90% damage reduction you still do 10% of your DPS)
- nuke the 3 big adds, thus getting the 3 stacks of Lightning charge
- kill boss within the 30 seconds of the debuff
