This really depends on what dungeon you're running (got a DRG before DD? Yeah, you'll never see AoE out of him cause he HAS no AoE) and what DPS the melee is (DRG and MNK should AoE for 3+ mobs, NIN should Katon for 2+ and AoE for 4+ cause theirs sucks so much). Then there's the TP issues and exactly which pull it is and whether the tank is slowing down to let TP regenerate (right before a boss and tank isn't stopping? I'm not wasting TP I'll need on AoE)

Yes, there are melee who won't AoE. I've also seen SMN who don't know what Bane is and BLM who can't find their Fire II (but can find Freeze...yeah, I've seen some weird things), and BRD and MCH who can't seem to figure out they can AoE in their caster stances.