I know to play seasons you need to be online.

But in terms of couch co-op, which is what I mostly play, you dont need to go online. Sure every now and then a patch will come out that will need internet connection but aside from that I dont really play online.

We did take some people around to fast level them but that's it. I dont play with random people.

Modded gear in D3, for me, wrecks the game.

Maybe back in D2 the developers werent bringing out new improvements and maps etc every few months like they are now and mods were needed to keep things interesting. But in D3 I've had gear nerfed thanks to modders ruining the game.