The problem with Cogliano is he's a cap dump. Dallas has never paid for another team to eat the salary of an overpaid player. They've taken another player back to get rid of guy, but that defeats the purpose of creating cap space. Nill has actively come back with overpaid players who had under performed to the detriment of the team in fact .... Niemi. So yes Cogliano makes the most sense, but it's not as easy as just saying trade him. A buyout doesn't make a ton of sense with him either. While he would absolutely be my first choice to dump, realistically, there's not much optimism that occurs. If Dallas is able to shed his salary, Nill will have either done something out of his norm or we've just shuffled the deck and moved him for another overpaid piece.
Comeau, at least IMO, isn't getting traded. Yes he's slightly overpaid compared to Cogliano significantly being overpaid, but more so than Cogliano he's become a fixture in the leadership core and they seem to really like him. If they were choosing between the 2, I'd be surprised if they chose to move Comeau first. Right or wrong, they seem to think he is an important part of team leadership.
Just because of the structure of his contract, the guy that does make some sense as a trade piece, especially if you wanted to keep Faksa, is Radulov. He's due a large bonus on July 1, and his salary for the remainder of the season is $1 million. He only has trade protection against 15 teams. He's due $4.65 million the final year of his contract, and a buyout is not cost prohibitive.
Regarding Faksa, he definitely makes the team better. He's also excellent value at his current contract. He's about to get paid like Hanzal though, and despite getting PP time, even if he is saddled with Cogliano and Comeau at ES, he's still not producing. There is very little doubt in my mind that he will become a difficult to move, unwanted contract sooner rather than later. The exact way we're talking about Cogliano and Comeau is probably where Faksa will be in 1 to 2 years.
Defense-first centers with little offensive ability are cheap to acquire via trade, and they shouldn't cost that much cap space. IMO, this is the unfortunate situation where yeah Faksa makes the team better, but he's no where near worth the value of the contract he's going to sign. If you had nothing behind him in terms of prospects, you might be forced to sign a longer term deal. However, you have Dickinson already in the NHL as well as Dellandrea and Gardner who are close to NHL ready to fill that type of role. You also have a pretty solid defensive center prospect in Back who is a few years away. This isn't a position of weakness for Dallas, and those dollars could go a lot further addressing another area. Plus, you have the added bonus of the fact Faksa has value. It's not going to be astronomical, but he's a decent trade chip.
FWIW ... he is an under-performing Cody Eakin. It's actually kind of funny you used him as an example. They have almost identical stats with Eakin getting a slight edge when you compare their career path. Eakin, like Faksa, was extremely valuable up to the point he got the contract eating into UFA years. This is the norm for that position. Checking line centers get overpaid as they approach UFA, they either maintain their average scoring or more often actually see a drop in production, and then they become overpaid, bad contracts. We're already watching Faksa have his dip in production, and you have an opportunity to not be the team that overpays.