Passing Thought - Skills and the Expected Outcome

What are the possible outcomes of a skill check? Most systems have a pass or fail, some have some kind of critical pass or fail, and some have an auto pass mechanic for certain checks (Take 10 or Take 20), and some notion of a difficulty rating.

The way I see it, when looking at a skill check and assigning a difficulty, I have in mind an expected outcome. I then assign the probabilities to likely produce the expected outcome. The expected outcome could be success, failure, partial success, etc.

It recently occurred to me that there's a needless step here - really, all we should be rolling for is whether we got the expected outcome, something worse, or something better.

Here's what I propose: roll 2d6. On 5-9, the expected outcome occurs. On 10-12, a better than expected outcome occurs. On 2-4, a worse than expected outcome occurs.

I think that this, combined with a page of guidelines for the GM, would be a pretty elegant resolution mechanic.

Just a passing thought, but I think I'll develop this more.