I don't understand these Nasus changes.
Edit: I'm mainly talking about giving him a 50% reduced cooldown on Siphoning Strike whenever he uses his ultimate. The Spirit Fire changes are explained nicely. http://na.leagueoflegends.com/en/news/game-updates/patch/patch-715-notes
All this does is over-reward him for refusing to interact with his lane opponent and reaching level 6 as fast as possible. He still will be garbage if he's set behind, but now he's even more oppressive if his duo jungler gives him a kill. These changes just turn him into a "win-more" type of champion.
What they should really do is give him the means to obtain a powerful late game through tactical skirmishes against his enemy laner. I believe this was what Riot intended when they changed Veigar, allowing him to obtain free ability power by poking his opponents. This way, the lane doesn't feel like a boring farming simulator until he's able to 1-shot someone.
I don't have a perfect answer as to what a "pro-interaction" change to Nasus would be, but I'd try something along the lines of increasing his lifesteal against champions and halving/removing it against minions. This way, he can't just sit around and farm all lane, but will have a much better chance of trading favorably with his opponents.