The main problem with AoE is the PvE part. But if you cap it, there will be "Zerg" problems with PvP. So why not only cap PvE AOE?? And when in Cyrodiil the cap will not exist. Simple.
I Just dont get it.. Cap AoE... (Maybe its OP in PVP since you got 100 targets, I dont know...). In PvE AoE it is the only job of DPS... why cap it.. Its like having a cap on heals and/or on armor (oh yeah there's one armor... "my bad").
Well then lets cap Heals...
Anyway anything else is cap in ESO...