If you had more players fail to come close to their ceiling -- maybe because the combination of makeup, health, stamina and the team's coaching/training fails him -- it'd be more realistic.
If players could exceed their ratings occasionally, as they reach age 23-25, that would be more realistic. I'd swap that for the DITR, which usually produces guys who are in their 3rd year and 20+ points from their ceiling.
There are guys whose ratings suggest they are borderline major-leaguers, and one year they hit .300 or post a sub-3 ERA. The same should be built into the "fuzziness" of the draft ratings.