The Defiant Class design, for instance, demonstrated vividly the difference between a vessel designed primarily for exploration and one designed primarily for combat. While the war was over and diplomatic and scientific discovery needed to resume, Command decided it was not about to grow lax and so called for a vessel with a compact design and significant combat capabilities, like the Defiant, that also had the capacity to execute scientific, diplomatic and explorative missions on a small scale, when larger explorers were not required.

The Diligent Class was the resulting proposal. Equipped with the latest technology, including bio-neural circuitry, new sensor suites and propulsion systems, at the expense of being somewhat larger, it represented an overall improvement over the smaller Defiant Class in terms of non-combat mission interoperability, while still maintaining nearly the same combat potential. However, this vessel is not designed to replace the Defiant class project, but to supplement it and other small vessels designed for short-range exploratory missions. It sacrifices the heavy pulse phaser cannons and greater maneuverability of the smaller vessel for a high top speed and creature comforts for its crew.

Compared to the Defiant, crew accommodations are increased greatly over the older class; officers ranked Lieutenant J.G. and above have their own staterooms, Ensigns, warrant officers, and chief petty officers share bunked quarters, with one other person, while petty officers and below share quarters with three other crewmen. The starship is equipped with two holosuites as well as a fully equipped mess hall.

The ship is also equipped with two sets of VIP quarters and a conference lounge, facilities not featured aboard a Defiant, Raptor, or Saber Class, which makes it capable of undertaking diplomatic missions between two to three parties. This capability, combined with her impressive weapons array, makes the Diligent suitable for second or third contact missions with new races or to mediate disputes between small space faring powers. In essence, the Diligent has the ability to ‘fight her way out’ should negotiations fail.

Medical systems take heavy inspiration from the Nova and Intrepid Class starships. They include one standard sickbay module, with an attached medical lab, as well as a secondary ward and morgue. There are also provisions aboard to convert one of the vessel's standard science labs to work as a medical lab if there’s ever a medical crisis. The ship takes a cue from the Prometheus Class in having full-ship holographic projectors, to allow the ship's EMH to work anywhere on the vessel.

The Diligent's warp propulsion system is based off of innovations made by both the Intrepid and Sovereign Class projects. The warp coils are based off of a scaled-down Sovereign platform, while the warp core is a dilithium swirl chamber, based off of the Intrepid Class design, which allows for excellent power and speed. The warp engines are mounted on variable orientation pylons. When not at warp the nacelles are held close to the ship, minimizing the ship's target profile from the front and rear. This affords the nacelles some amount of protection since they are less exposed. Shortly before going to warp, the nacelles are deployed to help create a warp field that does not harm subspace, similar to the way an Intrepid Class vessel's nacelles pivot upwards prior to engaging warp speeds.

While the Diligent Class boasts notable improvements over the Defiant Class, and other similarly sized vessels, it is not without reproach. Designers were unable to find a way to install impulse engines capable of making the Class as maneuverable at sublight speeds than its smaller cousins, for instance. Instead, the Diligent relies upon complete weapons arc coverage, hence the reason for the large number of phaser arrays incorporated into the design. All of the vessel's torpedo launchers are capable of launching a complement of standard Starfleet probes, negating the need for a specific probe launcher. During war time, these would be replaced with additional quantum and photon torpedoes.

The vessel's single shuttlebay is not fitted for carrying fighters or large runabouts; a typical Diligent Class ship carries two shuttles. One of the shuttles usually doubles as a captain's yacht, owing to the fact that the vessel is not equipped with such a craft.

Typical missions for the Diligent Class include border patrol, light exploration, convoy escort, and tactical interdiction. It is not suited for duty as a deep space exploratory vessel with missions longer than a year, due to its size, but it can certainly handle more local missions based out of a starbase or deep space station.