I'm not very experienced with SMN ( I have it at 50 with a relic but haven't used it much in endgame) but I don't see how they have amazing AoE. BLM has amazing AoE, yes. All I can think of for SMN is Shadow Flare and Bane (which only spreads to 2 additional targets max iirc - maybe 3 additional).

I'm sure SMN is capable in AoE, but I'm not seeing how it can be considered to "decimate" our AOE.

Most people, it seems, underestimate MNK's AoE prowess. It isn't amaze-balls, but it's pretty potent.

Ultimately, I'm not too experienced with SMN DPS to make any reliable comment.