I have no problem with it...you see, no one had a problem with the Thunderstorm skill in D2 either. And do you know why? Because, although it always hits, deals a ridiculously low amount of damage (compared to other skills)...
So why would the Disintegrate skill be any different? It's actually worse, if you think of PvP.
So 1: you have to stand still while casting it, which make the Wizard a lot more vulnerable.
2: I doubt it deals full damage from the moment you cast it.
And 3: It may actually not be that cost effective...if it drains your mana like Baal shooting flames then I really don't think we have a problem here.
The only 2 great things about this skill are:
1: Great finishing move.
And 2: Good, maybe quite awesome for PvE if you have someone or something tanking.