User blog comment:The5lacker/Varus is not a normal AD carry/@comment-4452268-20130615004005/@comment-8256051-20130615113054

Varus AP would still be a DPS champ, not a burst champ. AD doesn't mean DPS and AP doesn't mean burst per se. (Urgot, Ezreal are AD burst, Teemo is AP DPS too)

Here the big problem with Varus AP would be that he would deal magical damage, thus making the job easier for enemy team that wouldn't have to tank physical armor alot and focus more on magic resistance.