right now the best way to level if you dont have a party for whatever reason (all your friends quit, they have jobs, you woke up at 3am and you cant sleep, your friends are a million levels ahead of you) feels like

1)Do leves
2) play a different game while waiting for behests to pop.
3)do behests
4) repeat 2.

there is no engaging storyline there... or even a difficult fight.

edit: or browse the forum while waiting for behests to pop, which is what i'm doing right now.