Vortex pinnacle. None of the trash or bosses is all that challenging (the stars hit for huge amounts of damage but they got nerfed and die pretty quick). Followed by Throne of Tides (none of the bosses are hard but the packs of trash before the mindcontrolling boss are. Damn huge packs of gilgoblins thta do retarded amounts of damage.) and Lost city of Tol'vir (the trash is easy, but the 3rd boss is fairly challenging).