When you cast a spell, it will finish the animation associated with it, even if you move (which will interrupt the spell). This is true for all spells. It's of course most obvious with ground targeted aoe spells like Benediction and Storm. However, this also applies to instant cast spells such as black fang and detonate. If you cast it and move before the animation is over, you will fire a shot that deals no damage, and your spell will not go on cooldown. This also applies to basic attacks; attacking with an essence requires you to stand still for 0.6 seconds (1.66 attack speed) for the animation to finish before you will deal the damage. This is precisely why a crossbow is the ultimate weapon for kiting, and why bows are absolute trash in comparison. Imagine you have to stand still for 0.8 seconds each time you do a basic attack while kiting, even slightly longer for "instant" cast spells - you do deal double the damage each attack, but the problem is that whatever you are kiting will kill you in between shots.
Edited by Alteration, 26 May 2014 - 18:39.