Buddy, when you are at lvl 2500-3000 trust me, lvl bosses are way better than pvp. You know why? You don't have crowded list of players like you had at lvl 1000 or so. You got limited players (5-15 maximum) to pvp, thus "wasting" stamina on bosses, helps better to lvl up. And challenges/outbrakes of corse.