a few funny problems with trying to figure out the fleets of these franchises.
Producer intentions have changed over time; originally, it was said that there were a dozen Constitution class vessels, and they seemed to be all that Starfleet was made up of. Later series make this as good as impossible.
Then there's the question: What does it take to defend a star empire? Do you need one ship per system? A fleet stationed in every system? What is it going to cost you to run your fleet? Are you going to use a few large ships? Many small ships? How much smaller/larger? What about your logistics vessels?
Many of these questions haven't been considered very carefully in production, so it's no surprise that the answers to these questions seem to shift with every new series. Money to build models often ran short, as well, so we're faced with the frequent re-use of a handful of models. While the TESB novelization calls for smaller Imperial ships to be present at Hoth, none were built by ILM, and thus none were present in the film. The same Klingon battlecruiser has been seen in every single series of Trek.
The question then is: How literally are we going to take what we see on the screen? It's absurd for the same model to be used for a dozen different sizes of Birds of Prey. Statistically, the Empire clearly doesn't have anything between a shuttle and a Star Destroyer. Is this reasonable? On the other hand, are the other classes even important?