I see the thinking behind a 3-5-2, we have at least three players who fit as a wing back, and about five or six centerbacks of similar quality, except for Jones. Allows us to have two strikers on the field and a midfield three, but it has to be executed right, which it wasn't. Not sure Jones is good enough either, in theory he should be as a the ball playing cb, but I have a lot of doubts.
In terms of guys going back to MLS it's only certain cases that bother me. Like Deuce said, Dempsey's was a good move, but someone like Bradley going back in their prime has already hurt us. Altidore and Mix are weird cases, Jozy fucked himself over by choosing a club (and league) where he was never going to succeed, and by the sounds of it Mix didn't have many great offers in Europe, according to Klinsmann at least.
Fortunately, it seems like our best young prospects are heading to Europe. Rubin and Flores are already there and a few of the U-17 kids are going soon. MLS is a decent place to start for most, I just hope they don't get coerced to stay once they're in their early 20's. We've already seen Luis Gil stagnate because he's in a side with one of the best players in the league at his position.