Those Quad-Engine abominations should be called Frigates. Stargazer and Reliant seemed like they were both built for the same kinds of duty. The Ambassador Class (and a couple of more modern tech skins) should go into the Cruiser Tier left vacant by that move.
In fairness the term 'Frigate' is not very well defined. Originality they were fast, maneuverable coastal vessels. They then became fast, ocean going ships capable of independent operations (What we think of as Cruisers today). In 1793 the US put to sea six Frigates that we might call a Pocket Battleship or Battlecruiser today. In the World Wars they became small escort ships unsuitable for the open ocean (but never the less deployed on it). Between the end of WWII and 1975 what the US Navy called 'Frigates' were really guided missile cruisers (some nuclear powered!) Today its back to small escort ships.
I kinda like calling the Ambassador a 'Frigate' since it comes from a time when conflict with the Klingons was winding down and the Federation might decide to call a Cruiser a 'Frigate' to make it sound less threatening, much like we did after WWII.
My Romulan Liberated Borg character made it to Level 30 and beat the (old) Defense of New Romulus with the skill point bug.