And the starts for those 5 starters were:
Lackey: 28
Lester: 31
Beckett: 30
Wakefield: 23
Buckholtz: 14 (mainly due to injury)
dice got 8 and Miller got 12.
You would have to analyze it across baseball in order to get past the injury issue, which I pointed out as being a major wild card, but an easy place to start would be with teams #1 and #2 pitchers.
I think it you look across baseball you will rarely find the SP past the #1 and #2 guys on MLB staffs with over 30 starts. However in most cases the #1 and #2 guys will have at least 30 starts and it tiers off from there. If a team 1 and 2 are the only guys that are going to get over 30 starts it stands to reason that 3, 4 and 5 are getting less with your least capable SP getting the fewest starts.
Of the three teams you used in your example only one really had a high degree of balance in starts, that being the Yankees and everybody knew that their SP was CC and pray for rain so pitchers 2-5 were a toss up. However even their only two pitchers had over 30 starts....CC clearly the ace and Burnett, the guy they had such high hopes for, dashed once again.
Of the 3 teams you choose the Rays provide the best example with their 1 and 2 getting 33 and 34 starts respectively and the only 2 with over 200 innings. Their #5 only got 23 starts and 135 innings. Their 3 and 4 both started 29 and finished with 180+ innings.
I should also point out that the number of starts and to an extent the number of innings pitched are the only stats indicative of which pitchers a team believes gives them the best chance to win, game in and game out which is how the SP are ranked through the season. The other stats give you the results of those decisions.