Warrior does it right, mostly anyway. I sure a few of you remember pre-nerf Skull Grinder back when it was nearly instant cast, that was pretty bullshit. But otherwise I think Warrior is the best example of good visual cues.
Mesmer, Thief and Revenant has some of the worst visual cues.
Necro has several skills that should have better cues though, but at the same time Necro is also the class with the most cast time in the game. Should probably be fixed anyway, it's better if it becomes weaker if the result is a better game