My players hit lv 12 recently (it's a long running game and they didn't start at lv 1).
Their AC are 34/36, 34, 32, 32 and 31.
If I wanna populate a dungeon I obviously will not put a bunch of lvl 12 enemies everywhere as this will end up being too difficult.
So I'll put enemies within the -4/-2 range.
If they are -4 and they are by the book (so I don't boost them to compensate which would make them more powerful anyway) their average to hit requires a roll
of 11/16/20 to hit the lowest ac. With the average AC it would be roughly 14/19/20 to hit. Meaning enemies rarely hit the players making plowing through them very easy
If they are -2 we have 8/13/18 for the lowest AC and 11/16/20 for the average. First hit in average has 45% to hit then it goes downhill. 45% ain't too bad but afterward it's very unlikely they will hit.
The players being able to hit a -2 in average with 7/12/17 for the lowest to hit of the group (beside the casters) and -4 being 4/9/14. Unless I fill the dungeons with lvl 12 or so enemies the players just plow through the encounters.. am I missing something?