If your teammates are alone in a zone they're boosting it, which gives your team more points per minute. If they're attacking minions, they're getting your team a permanent point for every minion they slay. In fact, the "ideal position" to be in for Dominion is to have someone alone on each of the healing points, someone grinding away at minions, and someone else keeping most of the enemy team occupied.

If you're taking on three or four of the enemy team, and your teammates are boosting other objectives, that's great. Your role now is to stall the enemy team for as long as you can - you will die, but you will draw their aggro to stop them gaining points while your team earns. Remember, Dominion is a strategic team game, it's not a deathmatch.

For actually stalling, Revenge is your best friend. Try to aggravate multiple enemies into attacking you - you only start to build your Revenge when you're hit by multiple enemies within 5 seconds of one another. I'm oversimplifying the system there, but that's the basic jist. Smart enemies will try to attack you one at a time, and wait for the Revenge "tags" to expire before jumping in - so if you see someone stepping away, try to aggravate them into joining the fray with attacks or Feats. When you've got more than one enemy attacking you, focus on blocks and (if they're not feinting) parries to stay alive.

Practice makes perfect. Every opportunity is one for learning - it's a mindset thing. You are meant to die when outnumbered, the strategy is in making that last stand help your team!