Thanks for the comments guys!
I know what you mean that it seemed to much like just a rectangle block, I've been experimenting a bit with adding some 'vertical stuff':
You can see that the 'vertical components' are kinda similar to the tail thing of my , which is kinda funny since that original escort formed the basis of . I'm toying with the idea that from a background perspective all these ships have the same 'origins' if you will, an empire or something that originally produced some specific designs (compare it to the STC in 40k I guess). This empire eventually collapsed, and new, and smaller, ones raised from its ashes. Now these smaller empires don't all maintain contact with one another, meaning that their technology might also develop in different directions. But despite of this there would still be some markers here and there that would make them seem somewhat similar.
In order to give the ship some more shape, I've also thinned out the front part (everything in front of the Distortion Drive) a bit. Some more detailing will have to be added, but that has to be done anyways!