Is it normal to feel overpowered in Diablo 3?

So I chose the highest difficulty as a new player (Hard to Expert). When I played the necromancer class, and got up to around level 15, I felt like the game was too easy for me. I realized it may have been due to my "pets" (skeletons), so I made a new character (wizard) to see if I'd still feel overpowered. I get to level 15 and the same thing happens again. I'm able to take out enemies like nothing, even the mini bosses in under 10 seconds. The question is, will it get harder as I progress?