https://www.youtube.com/watch?v=z9gG9oZ--H4it doesnt tho. in theory haste from different sources stacks multiplicatively but haste from gear is a single source.
Level 19 Human Warlock | WoW World of Warcraft Armory Profiles | Masked Armory is my warlock
So in that case, you think it is worth getting DPR. I'd lose 6 int but gain 3 haste and 3 crit. And the thing is I'm not technically going all out haste because my gloves and bracers are enchanted with spellpower.