The Defiant class is probably the federation equivalent of a battlecruiser or fast attack craft, fast, and heavily armed and armored for her size. She played a vital role in ending the war, but only because of who was in command - Sisko. Nontheless, as mentioned above Defiant was parked at DS9 half the time instead of always off on missions or in combat. DS9 could have provided a permanent crew (and logically should have, but that would have required paying more actors...etc) for the Defiant with only one or two senior officers riding along for missions.
That Defiant was only used occasionally for the war effort suggests that Starfleet did not need every ship out on the front all the time.
That Defiant was only used occasionally for the war effort suggests that Starfleet did not need every ship out on the front all the time.