Silithus is actually quite good imo. Quite a few quests there. And Burning steps is good for at least a lvl. Winterspring is good with some go kill X quests. Definately do Ungoro, heaps of kill X quests and such. Only a few collecting ones. Also, make sure you do the power crystals quests there. Only need 7 of each colour for each char, and the crystals are tradeable so you dont need to alt tab to loot. You hand them all in for good xp, then are sent out on 3 seperate quests to find a pylon (north, west, east) and get reasonable xp for handing each of those back in. Also, at least start linkens sword chain which starts from the wrecked boat somewhere south east of the middle, it takes you up to winterspring for part of it.

Have you done felwood? If not, do it now, at least 3/4 of a lvl there still.