Everyone that has ever played a caster, knows that when you cast a spell and your target just suddenly moved to the side from being in front of you, or swung around behind you. Your spell fizzles and nothing happens because the target for it has moved from the spells direct pathing. What i'd like to see is the spell being cast, is actually cast, even if it doesn't hit anything. That should not stop it from being cast, its just the target for it has moved. So like most other spells, when there is no target. Have the spell traverse its intended path instead of *Nothing*. I'd rather have wasted 2 seconds to cast a spell, and at least seen it go off, possibly striking something else. Than have it not do anything at all. Even when you succeed all your concentration checks. Ahem, tactical detonation, lightning sphere. If the target for its gone, the spell doesn't cast, but it'll still take ur spell points and go through the casting motions.
Another thing, when concentration checks fail, the motions for the spell casting continue. Whats the point there. Spell fizzled, we know it, monsters know it. Gotta finish the dance ? Can u cut that dance short if the concentration check fails? I'd rather not waste precious time trying to run at half speed, when i could be running at full speed waiting on global cooldown.