I'm not sure wether this should be a guide or if it's an exploit. I think it's an exploit because you shouldnt be able to level this fast. But anyways here we go.
The place we're going to go is the Kessex Hills which is a 15-25 zone. I started here since i was level 18 and currently am up to 37. These events are a lot easier with swarms of people. Basically what it is, is there are events that go one after another. There are 6 MAIN events and 3 off random events near the main events. So you will go in a loop doing event 1 then 2 then 3 all the way to 6 and start over at 1 again. You can get through each loop in about 10 minutes total if you have a good enough group. Each event provides 700-1000 exp varying on wether you get bronze, silver or gold and how much exp you gain from killing things.
You will have to find the event that is going on first. There are 6 main locations shown in the picture below. Just follow the paths / take the waypoints to travel.
These are the MAIN quests.
Break centaur worker morale to prevent bridge repairs.
-Lower Centaur's morale to 0%
Dispatch the Harathi Lieutenants.
-Kill all 3 of the Centaur Lieutenants
Kill the Harathi overlord.
-Kill the Overlord
Stop the Risen Krait from building their army.
-Kill 4 Risen Krait
Destroy the bandit cannons before the ore shipment is ready.
-Kill 5 Cannons
Stop bandits from collecting ore for a centaur supply shipment.
-Kill all the miners
Defeat the champion bandit foreman before he finishes collecting ore for centaurs.
-Kill the Bandit Foreman