Pop quiz: Your ally just took massive damage and fell unconscious, what do you do? If you’re the leader this is an easy one; use one of your healing powers and revive your fallen comrade. If you’re any other role your answer had better not be leave him for the leader. When a PC falls during combat it’s everyone’s responsibility to bring him back into the fight – not just the leader. Admittedly the leader is usually the one that can revive unconscious PCs easiest and fastest, but you’re part of a party, a team, and everyone should look out for one another. Don’t shrug your obligation to your teammates and let a dying ally make death save after death save while you keep fighting.
Now I know there will be times when it might make more sense for the striker to keep attacking or for the defender to just keep the bad guy locked down, especially if either of them has an incredibly low Heal check, but these should be the exceptions. Regardless of circumstance unconscious PCs should not be forgotten or ignored. Dismissing your dying ally is the same as leaving him behind.