I don't know your opinion of Enterprise (and frankly I don't care), but "In a Mirror, Darkly" created a different insignia for the Defiant crewmembers.
It's true that every Constitution class we've seen has a different insignia and the intention seams to be every ship has it's own logo, though for all we know each of those ships was head of a different fleet, so there's enough wiggle room for all the theories preposed.
However, my problem with the one-ship-one-insignia-each rule is that from a purely design POV, when you have a fleet in the thousands it gets harder and harder to come up with simple, distinctive and recognisable shapes before you start recycling and adding minute variations. With the NX-01/NASA style patches it's much easier, you can play with colours, shape have the ship's likeness and name actually written on the thing, not so with an abstract shape. Even so, after a while the shapes loose all meaning and you may as well wear a patch that just says "USS Enterprise" or better yet the registry number.
This may be the real reason Starfleet switched to a unified insignia, maybe not.
These are absolutely beautiful, Reverend... my favorite is the Nova Squadron patch... just awesome stuff, all around.
I'm quite proud of that one too, it's the first time I've been able to get vector to really look like rasta.