jep, it is hard to hit a target, but I had that myself too. After playing trough whole nm you sure will hit anyting you want. I sucked at it first, but now i am quiet good with my pally, he's lvl 82, and not even maxed, cause I missed the part that concentration pumps up hammer, so I went to do concentration when I was like 70, so it's not so high. despite of all that he totally rocks, cause he's fun and because I played so much with him he even is superb in hell. I can dodge everything, and still hit anything from a distance. it will just come to you as you play, at first you just miss everything, then you hit everything that stands besides you, and after all that work that's called playing youll hit about anything you like.
and you'll get the hang of how long a hammer takes to get to the wanted place after a while, so the aiming isn't really that bad.