I picked the standard assault cruisers as my level 40 ship, so I'm trying it out a bit now. So far it has been very positive, though my gear is still horrible. (I rushed this character through with patrol missions only). I think I'm going to get the Fleet Assault Cruiser, I have access to a T5 shipyard. I'll skip the Regent for now as I just don't have the zen (but tons of EC for the modules from the exchange). Maybe I'll get it later for the skin and torpedo when I farmed up some dil. Though probably not since the gear I envision for this will be extremely dil intensive to begin with (Romulan Plasma).
The Excelsior sounds interesting from a stat perspective, but the design never clicked with me. It just looks different from any other fed cruiser, like an odd man out.
I actually already have two D'Koras on other chars. I love that ship. I fly it like a destroyer/escort with DHCs though. So it doesn't cover the playing style I'm looking to archive with this (for me - I know it can be flown in a more traditional cruiser style too, but why fly the same ship three times when there are so many options I kinda already regret the second as too much)
I'll get back to you folks with a build to discuss tomorrow. My eyes are bleeding from 4 hours of patrol missions. "Kill 5 squadrons of Jem'Hadar", "Kill 5 squadrons of Cardassians", "Kill 5....". I need to stop before I hurt myself :X