I've been using my 70 mage to push my 4 other mages through in SM (herod wing...whatever it's named). I can make 4+ bubbles on the mages per 15 minute run which is great considering I generally try to get a level a day and then go do something else (I'm seeing between 100 and 150 per kill in there with the nice 5man group bonus). I've done 27 to 35 in there so far (leveled to 27 using quests, but to be honest I HATE quests). If you have issues with the alts dying then leave them safely back from mobs and go kill with the main. At level 32/33 I could safely keep the mages with me and do 5x AoE

Might try pushing them to 36 or 37 there and then go do the "repeatable" mana surges quest to get to about 44. It's up in the air after that.

Coming from DAoC where we always did massive grind sessions to PL alts I'd rather do it this way than quest.