You also have to keep in mind that other various factors come into play.
For example, When I play DRG or SAM I can sometimes over power the tank. Sometimes they can be under gear or really don't know how to tank. Normally when I don't aoe is do to this or that one of the mobs has an area aoe ( Minatour or Chamira ) were I focus on it and stun accordingly. ( Sometimes you can't count on tank to stun or others to silence ). based on judgement yes we choose to not aoe. another instance is based on what level dungeon your in...I've come across players that are just lazy to do it -.-. Yes it's sad to see TP bars, it's even sadder when tanks over pulls knowing Mages have low MP and DPS has low TP.