User blog comment:TheTobarMethod/Do AP's Need A QSS Upgrade?/@comment-4290320-20130903161424/@comment-15244341-20130903192323

In a Teamfight, Orianna spams Q after her combo. That's where her popularity lies: in AoE, low cooldown spells with decent damage and utility that bring high DPS. Ahri does the same. She can do well in both teamfights and lane because she is less bursty than say, LeBlanc, but she still has a good burst which is in a low cooldown, unlike LeBlanc.

Actuallu, there are quite a bit of pure DPS mages such as Rumble, Swain or Cassiopea. They just aren't that favored right now since the don't usually have the safeness that some others do.