Nasus problems

I've noticed a LOT more Nasus players lately. So what's the real key to stopping him? Pressuring him when he farms isn't always easy. We all know how ridiculous that champ is when he gets to farm his Q. I just hate how I could get him to 0/4 (or whatever negative score) but he is still relevant because all he needs to do is press "Q" 200 times on minions and he's unstoppable.

When he ults he gets to spam his Q like a machine gun all while what seems like perma healing himself, despite gw. Is this even healthy for League? I don't see Veigar being as much of an issue as this champ, and they both have that Q farm thing going on.

Just him being in the match causes pressure. As a mid laner I roam as much as possible, but sometimes my lane is tough and I can't get around as much as I'd like. Sometimes bot lane is having a hard time and my attention goes there, or even to my own jungler who may be getting invaded. All the while Nasus is up top chipping away at becoming an unstoppable machine just for clicking "Q". Any sure way to punish people in game for picking this champ?