Not really. 90% of the time in Arena particularly you cant even cast a 0.5 cast time spell without being interrupted. Certain spells will get through ofc but the important ones will always be interrupted by skilled players. It is an unneeded buff though as I and many other players I see in Arena these days very rarely cast anything except in an "oh shit" situation but they're quickly locked out anyway. Casting is a thing of the past now that every man and his dog (goat? lol) has an interupt ability on a very short cooldown.