I still apply regen effects despite many of the ticks being wasted. Overheal is something that has to be accepted as part of the game. Also, WHM have no passive traits that rely on speed either.

Speed isn't universally reliable as it doesn't apply to HOT effects and healers don't chain heals off like DPS can chain their attacks. It can slightly improve reaction time, and helps in those cases where you DO chain heals, but this isn't all the time. There are other times when getting an extra 50% on the heal you're casting is more useful than getting your next cast a bit sooner.

In the end, I'm not even claiming that crit should be taken over speed. What I'm offering is some counter-point for people to think about.