There's an issue too where the flat d20 system makes the AC and +hit scaling really off in my view. If you go from only getting hit on 17+ to only hit on 18+ t

There's an issue too where the flat d20 system makes the AC and +hit scaling really off in my view. If you go from only getting hit on 17+ to only hit on 18+ then you are reducing your incoming hits by 25%, and the scaling only gets even more skewed from there. Whereas on a barely armoured wizard, going from being hit on an 8+ or 9+ barely makes any difference. In some sense it encourages specialism but on the other hand it doesn't sit well with me. Having extremes less likely would also help with this since you'd be cutting out a smaller chunk of the curve each time.