As far as I know It is almost impossible to hack/mod items on the PC version, and I have personally never encountered such a thing. I believe the gameplay on PC is about as fair as it can be. I've heard about the modded items on the console and it's really too bad that blizzard hasn't addressed this :< (I believe it may have to do with offline play? Idk.)
In my opinion this game is made for PC, and on the bright side you'll get all the patches and expansions much faster!
Haven't encountered any hacks or mods personally, don't think it's possible, on PC. I played for a while on Xbox One as it gave me something I can play with the girlfriend, on the couch, right. I'll take a moment and say hot damn is the console version tight!
Her friend decided to give her a few hacked items, like a ring with +10,000% damage, stupid shit like that, she went from Paragon 50 to Paragon 900 in an afternoon. I haven't played since, she's well aware she ruined it for me =/
I came back to PC because I like to play multi with randoms a lot and that scene was lame as hell with all the hacked items and dupers on console. I enjoy the gameplay on console more too, so that sucks, but oh well.