Spell Speed already increases DOT damage, though by a rather minor amount.
It does not decrease the tick interval, and that'll probably never change.

I wouldn't mind a merge between skill and spell speed, we are long past the days when one class might require a bit of both.
Haste already exists as a stat, so it's implementation in the normal game mechanics should be easy, right? Perhaps SE wants to reserve it for places where you can become an unstoppable force if you grind the right gear? Eureka and Bozja both feature it and you can become rather uniquely powerful there, though I wouldn't say it's due to haste specifically.

Something to think about I guess, but I'd like to at the very least just have skill/spell speed be merged to uh... "speed" I guess.