One issue stands out for me:
All of these kitbashes and other artistic derivatives, that people present as dreadnought-starships, seem to sport more weapons, more nacelles, and often more bulk, but there doesn't seem to be any more tangible protection. I point this out because one of the key features of Sisko's Defiant was a coating of ablative armor (whatever that was) wrapped around a simple hull design, like a turtle in a shell. Everything about Sisko's Defiant seemed non-standard. (Quantum torpedoes, armor shell, compact size, lack of standard Federation starship amenities, somewhat unorthodox nacelle configuration) By comparison, most dreadnought artwork by fans and FJ seems to use standard Federation components. Even the hulls look like they were derived for non-dreadnought starships. This seems to be universally true of all these fan designs, even my personal favorite (the relatively unconventional Kirov by Aridas Sofia
Why doesn't someone take the notions of Sisko's Defiant and apply them to the pre-TOS, TOS/TAS or TMP era to see what a heavily armored prototype Federation battlewagon would look like?