When I started running low level dungeons with friends that were overgeared and synch'd down, I also had some issues holding enmity. If you mean really low level ones (16-18 or so), then holding enmity doesn't really matter. You don't need tanks for most of those outside of boss fights.
For the rest, if you're slightly undergeared compared to the rest of your party, tell them to wait a couple of seconds for you to establish the hate. After that, you really shouldn't have adds pulled off you.

Also remember, it's everyone's job to watch the enmity. If some trigger happy dps is spamming aoe or hitting an add that's not the target, then it's their fault for pulling agro off you. Tell the healer to let them die if they don't want to play game. If the healer is spamming cure or physic when you're on 95% life, tell them to stop.