I don't think that the healing stream totems will heal enough for a life tap. I would say go priest for AOE. I run pally, priest, and 3 locks. I haven't really play the 3 locks and a priest yet (been working on getting the shams to lvl 70). In solo play i usually don't life tap every other spell. I try to finish the battle then tap away (got yelled at once for tapping with half mana, healer said to tap afterwards and he would gladly heal me, just tapping in the middle of battle is bad because takes focus away from tank). But sense you are boxing you wont really get yelled at. Plus tapping every other spell will decrease you dps. So if you are able to go the whole battle and tap at the end, then totem will be useless because there is so much health you need back, this is where the priest shines the most (granted that chain heal can get the locks, but it is reduced per jump). If you put you party in the right spot then you can heal your tank, after a couple spells do a couple life taps, then do a couple aoe heals to get locks back up and continue with tank. Also if you want you can do like 3 life taps and link that with a priest macro to put a HoT on the 3 locks.