This is pretty standard in the NHL as far as moving declining players on larger contracts...
Just about any successful team has had to, or will have to do it. It's the nature of a salary capped league. You don't hit on all your contracts, you don't hit on all your draft picks. As long as you hit on a solid number of them, then you're a successful GM. No world is perfect. In a perfect world, Hossa would still be playing, Seabs would be traded, and Panarin, Saad, Danault, TT, etc. would all be Hawks. Then again... that's not remotely possible in a salary capped league. Good players that you develop inevitably will move on to bigger and better things, making more money for other teams. You can't keep em all. Not even close. Most Hawks fans should know that by now after seeing cap purges after each of the three Stanley Cup seasons...