I was looking over some of monsters of CR 7. In the MM (3.5e), the average AC is 18.
I've got 3 PCs that are built for combat. Their attack bonuses are +14(archer), +12(Ftr), and +10 (WB/Mnk). So, on average, they should hit a typical CR-appropriate target 65% to 85% of the time with their...