Questing until level 15, then multi botting with QB and DB, imo. If you have multiple accounts you wanna level at the same time, and the sessions to do it, you can even link the accounts to do the same dungeons, make your q time a lot lower.
just run any bounty profile, with levelswap/armory or similar plugins to swap skills and equip while progressing.
start on normal for the first levels, then increase to hard/expert
