One with one, best system is to do quests, especially kill X. Followed by instance grinding. The advantage of instance grinding is you don't need to look for quests or follow guides. A 70 Hunter can in effect Solo up to BRD, or perhaps further if well geared. My own can certainly do up to BRD. Important thing to know is what is the starting level for a dungeon, not what level its intended for. eg Deadmines starts at 10, Stockades starts at 15... etc.

Other advantage of this is PLing an enchanter gives lots of DEable drops, tailors have lots of cloth drops. Or just sell everything for cash, in which case for Alli BRD and Gnome (also has mail box for re-supply) are good as both have NPC vendors in the center.

Or take an engineer with repair bots, but harder and more costly.