The USS Defiant NX 74205 Was a Federation Starship of the 24th century
This ship was a protoype for an anti-Borg weapons system, and as such lacked many of the amenities considered standard on other Starfleet starships.
She was equipped with quantum torpedoes, phaser pulse cannon, ablative hull armor. She was also designed to be easy to fabricate and build, allowing minor bases and backwater worlds to build copies.
Considered a "super attack ship" after her initial evaluation the Defiant class was firmly in the escort category. Too small to even be a light frigate. She had a punch out of her weight class but that weight class limited the vessel in any other role.
Defiants are found at border star bases, and as escort to merchants in insecure areas.
The Defiant was a mixed success. Excelling in anti-starship combat, she was too limited in other ways. Many starbases built Defiant class ships to act as military rersponse ships, but relied on heavier multi-role ships to get more complex missions accomplished.
Subsequent starship designs showed the lessons learned by the Defiant class.