I agree with those who are pointing to grip as the culprit. I disagree strongly with the idea that a certain amount of finger has to be in contact with the trigger in order to press it correctly.
The targets with the circle in the middle and the "pie slices" that go around it which show what error you're committing are next to useless. I've almost never seen somebody use one of those targets to successfully diagnose a problem and then fix it (the only exception being jerking the trigger).
Here is what I recommend you try: grip the crap out of your gun with both hands. This 60%/40% stuff goes right out the window under stress (assuming you are training to
fight with your guns). In reality, a stress grip will be more like 100%/100%, so just grip the gun hard. How hard is too hard? If you're shaking to the point that you can't keep the sights aligned, then back off. Otherwise, you're not gripping too hard.
Next, shoot this drill: at a distance of 10 feet, sight in on a 1" bullseye - a simple hand-drawn dot will do just fine, but you can print it up or use a 1" target sticker if you want. Take your time. Treat each shot as an individual shot where you pull the gun down from the target between each shot. Slow fire. Really focus on gripping that gun hard and doing everything you can to keep the front sight centered on the target.
There are a lot of people that deride the "white knuckle" shooting grip that I promote, but it works like magic. If I notice my groups getting a little loose, then I retighten my grip. If students can't quite get their rounds tight enough, I reiterate the same thing. It solve a LOT of problems.