The problem isn't that Haste scales out of control, the problem is that the devs haven't done a very good job controlling GCDs in MoP. Unholy is actually much better than most other specs in terms of free GCDs, but the haste cooldown breaks all that fine work.
@Jackthelad: Those options only work if your previous target isn't dead and the new one is close by. That doesn't apply most of the time. I agree that the ghoul rampup is Unholy's biggest problem by far, and so far the 5.2 changes have not addressed that.