Shouldn't he have been able to catch the arrow that Deanna hit him with in Q-Pid? And shouldn't his accuracy with a phaser be perfect or near perfect? I would think his marksmanship should be something that he would never alter as lives may depend on him killing or stunning another. And if it is simply at target practice, again no need to alter his ability, you're not showing off if it is something you can do.
I guess it's possible that Data didn't see the arrow coming.
Yes, Data's markmanship should be as close to perfect as possible. He should be much more accurate than Worf, Guinan, Yar, or any other humanoid in Star Trek.