No. You -CC- the healers and then focus the DPS. Otherwise you're just wailing on a DPS who won't die.
You ever played on an 8 man rated team where you can get 4 good DPS on a single target? No healer(s) can keep him up, unless there is also a guard and an AoE taunt to help.
But again, it depends on respective team coordination levels. If you can only get one or two people on the same page, stunning a healer first can work great.