GCD capping is annoying for sure, but it doesn't make haste significantly worse than crit when talking about single target performace. Haste still reduces the duration of RoF, and makes Chaos Bolt cast faster.
My theorycrafting doesn't show haste being worse than crit or mastery all the way up to 10k haste rating.
Obviously this only applies for single target while you're using Sup/Serv. Mastery is best by far if you're using Sac or AoE'ing for a significant period of time.