Ooooo! Hardcore anti-blood magic Wardens! I decided not to map that one out in my plot arcs because it doesn't really change Cullen. Instead, it just confirms what his new feelings about mages and he continues on the same trajectory.

Btw, there are a few ways to annul the tower in DA:O without killing Wynne, but I doubt that people normally select this path unless they are purposefully playing a "hell on wheels" warden or a warden who has deep anti-blood magic beliefs.