Quote Originally Posted by Havenchild View Post
Start casting Bio II, set up auto-attack immediately after you press the skill, watch as the auto attack goes through even before you finish casting that Bio II.
Not sure what your idea of "before you finish casting" is. That's when the cast ends but before the animation finishes. Which is not unique to any spell.

Ruin 2 is done to avoid the "can't AA because I'm casting" thing.