this build is all about split push power. ive found that nasus is not the best at ganking but what he does have is his Q farm for late game. if you dedicate your early game to stringent Q farming, than you can get your Q up to 400 easily by level 13-15. this requires a team that can be pretty self reliant lanes. around level 15 you can start pushing bot or top lane with impressive speed and the tank build gives impressive survivability when pushing lanes on your own. this build also allows for taking massive damage in team fights and is maximized when there is a lulu support who can pop her ult on top of your own, and at max, this puts your health close to 7k, making you virtually unlikable during team fights. i have had good success with this build though i have found that spirit of the lizard elder can be a good substitute for spirit of the ancient golem if you need a bit extra damage to burn through minions when pushing a lane.