If you can't afford good equipment, I should recommend you mystic.
Of course, tempest is more dps and pvp than mystic. But the second one is a healer supporter.
In fact, when you fight against elites or nightmare mobs, you will need a lot of defense or heals. And mystics can have protection totem, first aid, healing totem and healing fairy. And you can add dna to strenghtened or durability of totems.
I've played a tempest and my mp goes out really fast. And this doesn't happen with my mystic... Both classes have their cons and pros, but I would give the point to mystic for pve, and tempest for pvp.