I think they had the most fun laughing at me. I began gouping with them around the mid 20s with my rogue. I would stealth, then start sneaking up to the mobs for a Cheap Shot. Next thing I see are three mages charging past me yelling battles cries. By the time I tip-toed up to them, all the mobs were dead. So, I stopped stealthing and just charged along with them. Sinister Strike for one Combo Point. Sinister Strike for two Combo Points. Then, "Hey, you! Get up. I haven't even Eviscerated you yet!" Grr.
They quickly out-leveled me because while I was slaving away at work, they were AoE grinding. So, I jumped on my druid around level 32ish. Being the responsible player I am, I stayed in bear form to tank. After all, everybody knows mages are squishies and can't take the aggro. I charged the mobs and let out a ferocious roar (whatever that aggro builder shout thingy is) and start swatting the mobs. Except the mobs aren't anywhere around to swat. Yep, those squishies were tanking again. Grrrrrr.
I go to work the next day, and when I come home, the mages are now level 45ish. Gotta love that AoE grind. So I jump on my 45 shadow priest. Fort buff, Fort buff, Fort buff. Watch three mages AoE. Watch three mages drink. /Yawn. Rinse, repeat. Everything dies before they need healing. Everything dies before my DoTs take full effect. Grrrrrrrrrrrrrrr. Get bored, go play COD2.
There was a fun side to it all: We would chase down alliance that were 10 levels higher than us and send them to the grave.

For the Horde!!!!
Nerf mages. Uh, wait a sec. I'm leveling one now, diregard.