I have tried out playing the way you mentioned. Staring at my hotbar instead of the scenery. Didn't work for many reasons. This way I couldn't dodge AoEs, realized much too late I had to interrupt something and lost aggro from time to time. And yes, you do not exactly know when your animation is over. So why do it? ^^ Again, it ain't too hard to count to 2 to push the button, is it? (those were lots of "t(w)o" O.o)
But there is one situation in which it would be quite a help to have an indicator for the animation-lock:
Game gets too flashy. If there are 8 ppl using whatever skills they have and some or the majority of them are casters, it is most likely you start to have problems to see your character properly and thus his animation. That is true. Greying out abilities until usable would be an improvement, I agree with that.
I totally disagree with changing the combat mechanics. It is kinda what makes this combat system unique and, in my opinion, enjoyable.