The Deng deal is a solid deal, even at 4 years. He is versatile, and he can stretch the floor, and is a solid veteran. You could package Deng for a sign and trade or a straight trade and the other team might find his ROI fine.
The Mozgiv deal made little sense unless it was a short contract. Nobody will want Mozgiv when he is 33, 34 or 35. That contract just eats up 4 years.
I think that the logic behind the Mozgov deal has to do with Zubac as much as anything. Zubac is considered a first round talent that fell to round 2 because he was unwilling to be a "Euro-stash" guy.
I think the idea is that he can start and mentor Zubac for a couple of seasons and then come off the bench for a couple of seasons. Also, there's supposed to be an amnesty coming in the next CBA, so they can use that if necessary.
Interestingly, the word out here has been that Luke was actually more interested in Mozgov than the FO.