I think that it is worth nothing that DS9 allowed itself more to have a bunch of secondary characters, even it's format and storyline. ENT, considering they were always on the move (especially in its first two years), didn't.
Enterprise dropped the ball completely. Not only were half the gast being systematically ignored, but the show really did not have secondary characters. Shran, Admr. Forrest and Soval were more like recurring guest stars in the mold of Q or Lawaxana Troi.
This is a load of bunk, especially since you have on the DS9 list characters such as Damar, Eddington, Winn, Leeta, Bariel, and all the Ferengi characters among others. I would say they, too, were guest starts in the mold of Q or Lawaxana Troi. The only up screen time they got wasn't until season 6 and 7 when things started to get wrapped up.
Also, let us not forget the surplus of secondary characters in season 3 of ENT.
Also, look at what a secondary character does. The character adds to the already established cast, as opposed to a guest character where the character is the focus of the episode. Characters like Forrest, Soval, etc were never the focus of the episode and were there to add to what was going on.