I say for deer size animal, softball group 70-90% and your fliers hit a pie plate, you are within your effective range. I think consideration of not just what constitutes a group, but how bad are your misses is an important factor frequently missing from this discussion. I've seen some people in mentoring hunters where they'll zip in decent "groups" but their misses would be wildly bad misses. Reigning in those fliers fairly close to your group is important to work at. It's like in pitching the distinction between a harmless wasted pitch and a wild pitch advancing the baserunners, except life and death consequences.
Consistency from day to day also. I used to work on longer range shooting a lot more prepping for elk hunts B.P. (Before Procreating) and I would have days where I would be dead nuts at 70-100 yards and feel like I could reach out there like Cam Jesus Hanes and days where it was a struggle that would bring me back to earth. Don't go out there and shoot the best round of your life and feel your can stretch the field, you need to repeat that several times.