Good topic. Jason isn't the only one around here to have trouble discussing design in theoretical terms, but the longer you think about it, the more scientific you tend to get, a la almost any gca who has written some theory or another down. Witness, the king of intuitive design slowly becoming more scientific by his own admission!
Seriously though, nearly every gca does it, and all the old guys had to do it to write about their "ideal' course. The first chart similar to the one Mike Nuzzo posted was from Stanley Thompson, I believe, or at least, that is the most well known chart. But other old architect articles state that the starting point for variety is a variety of hole lengths.
As Jason alludes, its not just length, as depending on uphill, downhill, wind, up/down slope of LZ, etc. you might have a situation where consecutive holes with 25 yard length differences actually play with the same approach club due to those factors. I actually try to estimate those things with what I call "effective length", but they are just estimates. I know some say you can't figure stuff like wind out reliably, so why try, but I figure I am better off trying to balance approach distances to some degree, just to know what the golfer is likely to face in the real world, and then flesh out the green accordingly. While they may not hit exactly a 7 iron, its nice to know that even though a hole measures 450 yards, if its downhill, downwind, and a roll out down slope in the LZ, its likely to play 30-50 yards shorter.
Even so, I start with similar 20-30 yard splits on my holes, with my starting routing more traditional par 72, 4-10-4 and the par 4 yardages at back tee yards of 340-360-380-400-420-440-440-460-480-500. Par 3 can split 130-160-190-220 or so. As TD alludes the par 5 holes probably need a bigger split. That said, even mid hitting tour pros like Notah Begay still find 540-550 as tweeners, so I think his par 5 holes may be a bit long, angled towards the longest PGA Tour pros. If you want the old Gary Player idea of one reachable by all, two tweeners, and one true three shotter, it still might be 530-560-590-620 or so. If the top ten hit even the longest in two, so be it.
Of course, this perfect balance is only attainable on flat land, and the more the land rolls, the more variance I expect. That said, its not really as hard to vary the hole lengths to taste on gently rolling ground as some here may think. Push a tee a little up the hill, or move a green a little down or up, etc. Its often about the same hole in a variety of locations that are similar.