I think riptide is on a 6 sec cooldown, but last for 10sec or so? would take too long to figure out how many LHW's you can cast in 10 sec then recast.

Ive tried spamming heals on my tank but he just seems to go out of mana way too quick, resto doesnt seem to be real mana efficient for me, not as well as I would like it to be for boxing anyway. 95% of the time going OOM isnt going to hurt but on semi long heroic boss fights he needs the mana