Think about warlocks, in both PvP and PvE really. What are their strengths?

Mobility is the first thing that comes to mind for me. Dot and run.


Think of a paladin -- what are their strengths?

Standing there, taking a crapload of a beating, and just healing thru it with plate and bubbles.


Now think of a priest -- strengths?

Variety of heals - instant casts, big heals, aoe heals, shields, hots....


Now make an informed decision.