<<Morse is vastly overrated and can't adequately play the outfield.>>
My guess is that he primarily splits time between 1B and DH with Kendrys Morales. Jesus Montero didn't hit near well enough to be a full time DH last year, so they'll probably make him their primary catcher.
Jaso kind of got a raw deal with the M's last year. He was far and away the best catcher they had on the team (at least offensively), and I remember early in the year, Wedge kept benching him in favor of Olivo, who was hitting at Don Kelly levels.
I don't know if Morse will ever replicate the success he had in 2011, but the M's only gave up a player they didn't seem to care about anyway.
I think this deal kind of works out for all. M's get a power bat, A's get an upgrade at catcher, and Nats get a prospect.