I tested spell speed this evening.
Fast
2.23 seconds consumed
Frames to Effect: 14
Frames to Completion: 35
Frames of Recovery: 32
AVERAGE
4.3 seconds consumed
Frames to Effect: 53
Frames to Completion: 79
Frames of Recovery: 50
SLOW
7.93 seconds consumed
Frames to Effect: 128
Frames to Completion: 132
Frames of Recovery: 106
I used naked Wood Elves with 10 Dexterity as a baseline. Recorded casting in FRAPS at 30 FPS and checked speed frame by frame in After Effects. Dissected