I'm just a beardling but...

[Lileldys]

The way I see it is keeping your healers alive by focusing the enemy DPS. Once they can survive the few remaining DPS, then feel free to kill off some healers. Good healers will stack defensive stats as most heals don't scale well from Willpower. They will be harder to kill than squishy DPS
My Target Priority:
1.) Unguarded DPS
2.) Guarded DPS or Focussed Offensive Tanks
3.) Enemy Healers once your Healers can stay alive without guard/ST heals.

[Tenroc]

Again, you're asking to get over extended that way. Besides murdering DPS is the best way to keep their healers busy and your healers unemployed.

[porkstar]

My main observation is that an off tank should be snaring the main mdps 100% of the time. This is especially important with DPS DoKs. Snare, snare, challenge, snare, kd, snare, snare, challenge, snare and if you're good enough, throw a taunt on any healers or ranged you see casting some long cast BS. I like slice through on my knight when I'm playing this role. IMO snaring is just as important as DPSing that WE or whatever is in the front hacking away. Snares can really shut them down. And body blocking! Oh tha body blocking!