I don't think that what you are looking for could exist in reality.
The diastatic power of malt is undoubtedly important in determining if the base malts can fully convert the adjuncts if you use a large amount of adjuncts, but this diastatic power will be highly dependent on various other factors, such as mash temperature, mash thickness, mash pH etc.
Although it certainly won't give you all the information you need, http://www.brewingtechniques.com/bmg/noonan.html
does give you some information on this subject.
I must admit that I never brew beers with a high %age of adjuncts. (I have never exceeded 10%), but I use British pale malts to provide the diastase, and they provide less diastatic power than most other base malts. I'm sure I could theoretically use more adjuncts without any conversion problems, but that wouldn't produce the sort of beers that I like.