So lemme get this straight...

1.: 70(s) + lowbie enter instance
2.: Pala weakens mobs, kicks mage, mage novas mobs
3.: Pala runs out, mage finishes off mobs still unpartied
4.: Lowbie gets full exp?
5.: ???
6.: PROFIT!

Would the follow work?
1.: 70 + lowbie(s) enter instance
2.: 70 weakens them/aoes them down to near-death
3.: 70 is kicked from party OR leaves instance
4.: Lowbie(s) finish off mobs?

the latter would be hard if you pulled ALOT of mobs...unless they can aoe while taking the hits too(FNova/Frost-talented Blizzard or Barkskin+hurricane anyone?) and possibly a little time consuming buuut...anything that speeds up lvling