Dvang, I think the problem is the fact that after say 7-8 sessions should you really succeed at a Daunting 4D check over 60% of the time? That's nuts. Sure, you didn't include misfortune dice but you also didn't include stance dice which shift things heavily. I don't mind characters always hitting in combat, but when you move it to skill checks you lose a lot of fun by always having players succeed. Failure, often times, produces a more interesting narrative than success.
I don't have a problem with a 2d or 3d task being easy to make for relatively experienced characters. But how do you really challenge those characters with skill checks then if 4d is the cap?