I don't even use cloak on my fleet defiant because I tend to have far better consoles loaded instead, and swap them with others so I can keep chaining univ consoles.
Never been a big fan of the standard cloak.
Battle-cloak however, I love on my Hegh'ta, and it's part of WHY I fly a Bird of Prey exclusively. I have 1 less BOFF slot, 1 less tactical console and 1 less aft weapon. The idea of having a fleet defiant with a battlecloak is kind of ludicrous to me because it already leaves my Hegh'ta in the dust on so many levels.
The exhiliration of using battlecloak while tanking a tac cube in ISE is something I just don't feel when flying my fleet defiant. You need precise timing or you're going to be in trouble because you don't have a hefty hull.
Putting a battlecloak on the Defiant just sort of trivializes that... much like all the klingon consoles being trivialized because they're ending up in lockboxes now. I'm finding myself playing my Klingon less and less now days, and I can only imagine the massive exodus that's going to happen once (if) Romulans are added to the game.
Might as well put a cloak on the jem'hadar bug ship to be honest and put the final nail in the coffin on Birds of Prey. They're re-adding them soon, so they'll be pretty common.