This is really situational but found it to be insanely fast:

I had my warrior mass pull mobs close to the level of the AoE toon I was leveling.
I would AoE on the leveling toon and then use other characters to AoE/finish off mobs.

The PL toon would receive near max XP (not sure how this works - but seemed to be much higher than if the one char did a couple single target tags and then had others kill).

this worked great against elite mobs outside dungeons that I could mass pull. For level range was able to do 28-32 in about 20-35 minutes a level.