Ratskinner
Adventurer
It makes it so that easier tasks are really, really easy to hit and hard tasks are really, really hard. The strong central tendency to the dice probability makes your actual bonus a lot more significant.
The first part is just dependent on the DCs and where they are set (for instance, they don't have to be spaced evenly). The second part is the real meat of your thinking, and certainly true.
Sounds like a houserule/module to me. I'd replace d20's with 2d10. I think the 3e UA had a suggestion along those lines, maybe. You could use 3d6 (then you're playing GURPS

This is, of course, a matter of preference for anyone. Attaching adjectives to probabilities like "the average untrained untalented person can succeed about half the time" seems rather squishy to me. (Does that make it "Hard", "Easy", or "Typical"? Won't that depend on the type of task at hand? What about skills that don't make sense to use untrained?)