The first photo is tack sharp -- it's just that the focus is in the wrong place. You want the eye to be sharp, but take a look at the hair just above the ear. It doesn't get any better than that. It's hard to tell at the posted resolution, but I'd bet the base of the lavalier mic in the second picture looks as sharp at a 100% crop as it appears in this reduced-resolution image.

I know the Tamron 90. It is sharp, sharp, sharp from wide-open to f/11 or so, where diffraction starts to take over. It is only just the tiniest bit better at f/4 than it is wide-open. The problem is that you are now working with a camera that has a high enough sensor resolution to show focus errors that would not have shown up as clearly on the D60.

As your comment indicates, it's a matter of practice. The first thing to do is to figure out exactly where the autofocus sensor areas really are (the indicators on the focusing screen are only approximate), so that you can better control where the focus falls. Once you can consistently get the camera to focus exactly where you want the sharpest detail, you'll get back to loving the lens again.