No. If anything, the matchup will become more in Garen's favor with the e changes, and here's why. The e changes allow Garen to effectively take conqueror which is very useful agains Nasus as he builds really tanky, and the bonus true damage will really help in fighting him. The e changes also allow Garen to effectively use blade of the ruined king, another thing that will help him shred through Nasus.
The attack speed slow seems bad at first until you realize that Garen's q instantly removes the slow, meaning that if the Garen just holds onto his q until Nasus uses his wither (which you generally want to do in the Nasus matchup anyway), then Nasus basically doesn't even have a w.