Crit is a little problematic, in that it becomes less effective to add more the more you have. It works like this:



Plot of how beneficial the next % crit will be for a given % crit in terms of %dmg gained, for 200%, 175%, and 150% crit multipliers. I include the extra multipliers for no real reason other than it lets me put more pretty colored lines on the graph - that part just tells you what you should already know, that crit is more effective to add if you get a higher damage bonus from it.

Haste universally becomes MORE effective the more of it you have, while crit diminishes. There are periods where the rate it becomes more effective is slower, and there are periods where it is undesirable because it doesn't play nice with currently popular rotations. There are however more fun talents and such for working with crit, and it's easier to work with crit when it's in the earlier stages and hasn't run out yet. And who's going to get 100% crit anyway if they're not casting Lava Burst at the time?

So in brief:

Hit is cool until you have enough.
Crit is cool but eventually becomes less cool.
Haste is cool and becomes seriously OP if you get enough, but sometimes it's not worth what you have to give up to get it.