PVP wise, powertech >> merc because merc doesn't have so many tools to stay alive under melee attack (powertech can tank AND dps), so few and useless CC in many situation. If you have a group that keep you alive, merc can be devastating (arsenal one)
In PVP we have 3 maybe 4 heals. WZ med pack, power surge + heal. got a 1.5 casting heal and that can be lowered with tracer stacks plus a small dot, using all that and shield with the WZ thingy (red one) we can stay up ok when needed.