It really depends on how the AoE is set up.

If you're talking dungeon trash that allows for down time between pulls for TP regen, and dies fast because the whole party is doing good AoE, MNK is near the top. If it's large pack of dungeon trash that lives for 45+ seconds because the party sucks at AoE, a MNK can't carry the party through that like a BLM/SMN/BRD/MCH.

In the parts of A2S where there are more than 4 mobs in a cluster, BLM blows MNK away. When it's 2-3 mobs, MNK is basically getting bonus damage on their AoE oGCDs while BLM would end up doing about the same or less by going into AoE mode.