Healthier does not = better. The team is like 12-10 without Manu this year. Barely above .500. They're 29-9 with him. That's like .750.
Last year the Spurs missed Tony the whole RRT and did pretty well without him. And they didn't even Hill or Mason or Bonner playing a lot. Pretty much just Manu and Tim.
I think Tim is a top five player and the other two are top twenty players. This is why the Spurs will always seriously contend as long as all three are healthy. Without all of them at 100% though, they don't have much of a chance.