Realistically, I don't think an absence of Evolution would have affected Batista or Orton to much. I think they may have had to wait a little longer for their first title reign, but even that's only 50/50 to me because it'd probably have meant Trips would not have held it so long opening it for Orton (though Batista would have possibly been a little later).
Orton would have had more than enough momentum from his Legend Killer schtick to effectively hold a World Title; the Undertaker and Dad put Orton over huge. Batista, however, went from dumb muscle for D'von to dumb muscle for them, he'd have needed something else had he not been so ruthlessly endorsed by Trips and Flair.
I also accuse Evolution for taking Goldberg's steam. He had speared the Rock in his first 5 seconds in a WWE ring and won a World Championship in a month. I can still remember HHH punching a hole through Goldberg's brain in the Elimination Chamber with the sledgehammer and thinking "I've just lost interest in Goldberg and the Chamber all at once." From then on, Goldberg basically wasted his time until that embarrassing Lesnar/Goldberg match at Mania XX.
I think we may have missed out on one of the few meaningful World Heavyweight Title reigns we've seen since Bischoff brought it in.