1) Fight over objectives not on the road. IE fight on the flag or in the tower not in front of it.

2) Leave at least one DPS to guard objectives and call incoming enemies as soon as you see them.

3) Kill enemy healers. Chances are that warrior won't die before his healer does.

4) Protect our healers. They need to be alive to keep us alive.

5) Group up and try to stay with your group. It much harder to kill 4-5 at a time than it is to pick you off one by one.