The measure of whether a sight adjustment is needed (with ANY gun) should be the group size. If a person is executing the fundamentals of shooting in a sound and consistent manner, then the group of shot holes should be very tightly clustered on target, and the need for a sight adjustment should be apparent (as in your case).
If, on the other hand, the group is scattered/excessively large, missing shots altogether, or trailing-off in a comma shape, then proper applications of the fundamentals is lacking, and a sight adjustment is just as likely to move some shots away from the target center as toward it. This is one of the reasons that I've never liked that "group analysis target" that I see floating around the Internet; it does not take into account the size of the group, and automatically assumes that the shooter is doing something wrong based on a general area of the shot impacts. In your case, it would have been completely misleading, and could have cost you time and ammo money chasing a problem that did not exist.
I have NEVER seen a new-ish shooter who could slap/jerk shots consistently into a tight group. Same thing with poor sight alignment/picture, follow-through, grip problems, etc. The size of the group on target will tell the tale.
"If the group is tight, fix the sights. If the group is scattered, the shooter is the matter."
"Placement is power" -- seen in an article by Stephen A. Camp
(RIP, Mr. Camp; you will be remembered, and missed)