At that SS, the 135 should be tack sharp - you must have had a poor copy or that 100 is off the charts and you should try and re-buy it.
I think it may have been a poor copy, although the guy who bought said he loves it and is getting great results. Maybe his expectations are lower than mine were with it. But really I have no idea. I may have focused and recomposed as opposed to using the AF points, which is not really a good idea with this focal length and aperture. These were shot over a year ago when I was less knowledgeable than I am now. But yes the 100 seemed to be a particularly great copy. I sold it to a forum member in California who's no doubt loving it.