User blog comment:TheTobarMethod/A New View On ADC's IMO/@comment-98.246.3.43-20130211054252/@comment-128.230.200.87-20130211200851

That's not a caster. That's a champion using their kit to do thier job - which, in Vayne's case, is to continue putting Autoattacks into the nearest living thing. Casters would be Carries whose abilities comprise a significant portion of their DPS: Corki, Ezreal.