Text from old page, The Commonlands: Tons of quests for level 10-20 or so, many instances connected;

Valley Of The Rogue Magi (Requires Access)

The Prison Of Something...(Requires Access)

Wailing Caves.... good level 12-20 place.

Fallen Gate, can last you 20-30 with great loot, including end named that drops fabled items every time.