Again, there's really been no past battle that gave us the chance to see what and how the Defiant performs against cruisers. The fact of the matter is that there is no single way to know what counters what and how well it does so without priorly knowing what the ship's decent at.
I also balanced the sides based on my personal experience fighting gunboats in cruisers, which has been, summarized in one word, terrible. I have yet to win a duel against one, so it then only natural that unless those two Crecies are Haste tier of good, they'll succumb to 4 gunboats well before they even kill 1 or 2.
The balance on the bomber side was done while keeping in mind past battles (such as your fight vs me and Hemlocke in bombers in Connecticut some months back) as well as considering the large size of the Challengers that arrived.
