I am 49 now and changed out of frost into arcane and fire. It seemed to help me a lot..not only killing packs ( with the flamestrike to start..followed by arcane explosions and 3 blastwaves. ) but also solo mobs, not using pyro as i do not have PoM yet. But with flame blast and fire balls..bosses die in record time..if mobs are resistant to fire ( like stuff in searing gorge and burning steeps ) i use arcane missiles.