so what do you start on nasus then, ruby crystal or cloth armor or something? doran's blade maybe?
by the way it's very hard to play aggressively without pushing the lane, and having the lane push to nasus's tower is exactly how you let him free farm and then get ganked and still be unable to escape if you burn flash because the slow lasts forever.
honestly his early game SHOULD be god awful (which it really isn't that bad unless you're fighting a lane bully or a ranged champion, i've played nasus enough to at least know that.) I really wouldn't care about his later game as much if I felt like I could do more in the laning phase. Lowering his EARLY lifesteal and slow (like you said) is what they should change, and then they could maybe, as a compensation buff, increase his late game lifesteal.
with that being said, nasus is not who they should be looking at right now. they need to be looking at this
abomination.