Powertechs get tunneled over Mercs in solo ranked. A good Merc that know's how to kite and correctly use defensive cooldowns are tough to kill. If you play on Harbinger just ask Carthy, Stella or Asana how to play Merc. The 3 of them are fantastic at kiting and staying alive. I've healed all 3 and seen them take upto 800k in a single round in solo ranked ... The fault lies with you not the class.
As for who ever quoted me about Merc healers. Just roll a Sorc theres no reason anyone should be playing anything different. If Sorc healers get nerfed like everyone wants, no class will be able to heal the insane amounts of damage the game currently has. We all want that right? No viable healers? because even if Bioware buffed Mercs/Ops it wouldn't be enough.