A normal and smooth run:

1. Give one for tank as a healer, or healer as a tank.
2. If dps shows smartness by running to tank when they take over enmity and managing their dps cycle, kiting unexpected adds to tank, and never fail, I vote for the dps.

In short, I have a bit high standard for dps.

I never vote on:

1. DPS/Heal who pulls before tank. I regard them trolls, not even human being.
2. Anyone who does not communicate properly.
3. "I know everything and I am better than you." types.
4. Any role: failing their prime duty. i.e. healer fails to keep me up when I saw tons of stones flying into my target. DPS hitting wrong marker and running away from over enmity monsters, yet keep hitting it to end up healer distracted.
5. Not running away from that red circle(mostly DPS) and just waiting to be healed. Collateral situations (lag, oops 2 late, newcomer, that many reds!) excepted.