To "evade" implies that something is coming at you, and you move in order to avoid being hit or deflect the damage. So why does Major "Evasion" work on AOE skills? If you're in an AOE, then by definition you have failed to evade the threat.
Sure, that's just silly semantics but on a serious note the idea is worth considering. If you're making AOE's 33% weaker than single target attacks, then you should consider switching Major Evasion to a single-target damage reduction. AOE is already going to be greatly weakened next patch.