Levequests are now solo content that can be done in about ~2 hours by doing appropriate level quests. The exp from them is solo appropriate. So while looking for a grind party, or if nothing is going on, plow through them for a nice sum of exp and then you'll have them out of the way until the next reset.

I havnt fussed with behest since the update, I can't help you there.

Grind parties are a good source of exp that you can do whenever.

No fatigue means you'll feel less like you're being held back ever.

Level multiple classes to use their abilities on your main class like cure, second wind, defender etc

So, at 30 I suggest leves on your own free time for a short burst of exp. Then grind parties, usually raptors, beastmen, or efts. I still can't comment on behest. Also quests give exp now. And the main storyline quests give absurd exp. so much that I wished I hadn't already done them.