Boosting Question. Use my Shaman or Respec Priest

As the Subject says. Im wanting to boost a lowbie warlock to get up to lvl 25 to be with my warlock on my main account. I was carebearing the new lock with my 25 lock. which worked out good. Run and dot along the way. Succubus spanks the leftovers. Well then i got the alt to lvl 12 and the lvl 16-18 mobs were just a little too much to just dot up a whole crowd, they were killing the lvl 25 lock.

So I got 2 options. I can use my elemental shammy, which is slow as hell, cuz if they die by lightning shield or just totems the lowbie gets no xp whatsoever. Takes awhile to get thru the whole instance as well. Lowbie gets roughly 1/3 of a level in one run.

Or... Should I respec my 66 priest and use the old holy nova method I used to?

I think I answered my own question but any thoughts would be cool.

Priest is best option if you only want to boost to 25.

best bosters are

Prot Pal
Ice mage
Aff Lock
BM hunter
dual ax orc shammy