I don't really think so.

Art's department always seems to butt heads with everyone else. Remember when investigators were asking questions and Boyd warned one about talking shit about Ava, and Art backed him. And you look at how Art has always defended Raylan against investigators. And how often those seem to happen or be threatened. Look at how enemies of Boyd and Wynn like the cop Bennett, Walker, Danny Crowe, Tonin's hitman, and Quarles end up dead (or dismembered) at the hands of the Marshals. And how chummy Boyd, Wynn and Raylan are, and how when Vasquez brings up Boyd, Raylan discredits him as a threat.

And speaking of Wynn, notice how Wynn killed an FBI guy (Vasquez's boss). Wynn worked with Picker. So think back to when Art's office gets Picker, then he confesses - oh, now that Art's office has him, he'd like to volunteer that he conveniently witnessed Sammy Tonin kill the FBI guy who wanted to open a criminal investigation on Raylan. Shortened, chums of Wynn, who's chummy with Raylan (so, criminal friend of an FBI-killing friend), either killed or handled blame for killing the FBI agent who was most against Raylan. Sketchy.

Raylan's always done whatever the hell he wants. Art's always backed him.

So now, we have this girl Raylan used to be sleeping with, and she's been released from prison by the Marshals for the purpose of providing information, not only is she so useless they had to grab Wynn to do her job, she ran away and then Boyd found out she was an informant and Raylan still covers for her and keeps her out of prison, so he can, with the help of TWO informants, conveniently fail to apprehend a guy who he previously didn't even want to chase, because he claimed the guy wasn't a big deal. Raylan keeps failing to catch Boyd despite what should be a clear advantage over him and constantly defends a useless and untrustworthy CI who then, just so happens to get the slip on him, just as Boyd has just so happened to get the slip on Raylan whenever it'd work out better for the two of them.

Overall I don't think it's an unsound plot. I do, however, strongly feel they've underdeveloped it. It feels thrown in at the last second, Vasquez seems to flip from wanting to work with Art's office to wanting to bury everyone in it within the span of one or two episodes, with very little in the way of explanation. I wish they would have focused on this throughout the season rather than tossed it in at the very end, but I get the feeling they were more interested in trying to build up the Catherine storyline about Wynn betraying some off-screen character no one gives a shit about instead.