There are too many ways for him to get gold now, so he can get his items faster. His early game "weakness" really ain't so bad, and the window to shut him down is much smaller than it used to be.
Totally arbitraty number here. But let's say you had to shut down Nasus in the first 10 minutes to makes sure he wouldn't become a problem, now it's more like, you have to shut him down in the first five minutes.
Rumble used to be a Nasus counter, but Nasus can just get a
followed by
and laugh at his damage. Very early.
Edit: But to add to this post, yeah, i think they should either reduce his early sustain from passive, or reduce the number of stacks he gains from Q (2 instead of 3 on minions, and 5 instead of 6 on canons) Or at least reduce his split pushing power by cutting Q damage on turrets. The ability is called Siphoning Strike, a turret has no life force for Nasus to siphon.