All the third stage ones (except the leap) are the same total time before you regain character control. Basically you want to only use these in safe situations - thus is effectively her cooldown/balance mechanic.
Personally my favorite one is the burst that freezes everyone.
Ah, thanks for the clarification. I guess me thinking the glyph is faster was just human error. Anyhow,
There is a passive in the second three that makes you immune in the final stage.
Nothing can stop your casting.
Yeah, stopping the cast is not the problem. It's killing things quickly. Most third stages are pretty useless for that, though I'd like to add I've only taken her onto perilous. Maybe on nightmare the spells are more useful.