I feel ye. Not sure what a .5 + or - comes out to percentage wise but some of the extremes the game applies at times is rather ridiculous. I have a feeling it has a bit to do with the random generated BS which needs to either go or be adjusted (doubt if they will ever do it though). My accuracy and control skills are maxed out on approach and short game and I use the highest specs I can find for irons and wedges in those categories and it makes no difference at times.The balls gonna go where the balls gonna go. The most frustrating thing is when your total swing percentage is positive (red) and the ball still comes up 10-20 yards short. Like the game auto chunks or skulls you for no reason except the game decides it is time to do it.
I haven't tried turning off the swing plane yet and not sure I ever will, it is a crutch for me but on so many holes I can't even see the plane because it just blends into the sky. I wish they would alter the color. I use the modern setting so there is no little black line at the 100% mark and I have no idea where the end of the plane is half of the time. That won't fix the shot discrepancies but at least I won't get eye strain while playing.
I love the game too but these little things ruin it for me sometimes. Try doing a challenge where you have to hit 5 approaches to with 5 feet, you stop the swing in the same spot every time, the blue line pretty straight up and down and one ball fades right, one pulls left, one doesn't even reach the green, one goes over, etc. etc. More a frustration than a challenge.