#1 Lead the Charge ... this is simple I go in first and start hitting people, its natural they focus on me while the dps specs drop bombs and the healers keep me up without breaking a sweat. It works but it doesn't take long for the other team to switch to squisher targets.
#2 Pretend to be a Healer ... this is one of my favorites, instead of leading the charge I'll hang back and drop heals on my team. The heals aren't that big but they help and the other team tends to think I'm a healer and focuses me. Then the real heals and dps specs are free to do their thing. Of course this works better for pallies:P
#3 Taunt ... even if players are immune to taunt their pets aren't. Pulling a pet may not be much but everything helps. Also if the pets can be pulled far enough away from their masters they unsummon.
#4 Make them hate you ... sure taunt might not work but /lol can still get the other team mad at you. I've pulled people off nodes and into or away from incoming zergs of my guys just with a couple of /lols. This works real well in WG/TB type BGs where you'll be seeing the same guys over and over. Make them know you. Make them hate you enough to go out of their way to try to gank you so your mage buddy can toast them over and over.
Just remember this is just a game, no reason to ruin somebodies fun time with alot of /spits and rude comments.
Anyway thats all I've come up with so far.