AOE-acceptable,when?

[Sinth]

AoE on low-hp adds on bosses or on large trash mob pulls (so long as your tank has aoe aggro capability and have already established emnity)

[Seriat]

have already established emnity)

This is the big thing, as a tank far to often I see DPS just unloading on a mob the second my shield lob lands, and way before the mobs are even close enough to flash.

[Dyvid]

If the adds are weak and squishy AoE is fine. However if you aren't going to drop them fast with 100 potency hit then you're better off sleeping and focusing on the primary target.