Additionally, I have at least one (perhaps more) vessels with "Defiant-like nacelles", depending upon whether you refer to them being angled out or buried in the hull. The ship most closely resembling the Defiant's layout is the Longbow class, illustrated below.
I thought the Defiant with her nacelle configuration was a singular design until I saw the new scoutship. Maybe there are new unconventional designs to come, however, I think most of the ships will always have the traditional saucer/nacelle configuration, maintaining the design lineage and the Trek "Corporate Identity".
Frank, explain that xoom thing again - I can't see the pic
------------------ With the first link, a chain is forged. The first speech censured, the first thought forbidden, the first freedom denied, chains us all irrevocably." Capt. Jean-Luc Picard - The Drumhead