Players like Marvin Williams are what we need to take some chances on in my opinion.
He is still only 25 years old. A change of scenery may do him some good. Play with a PG that would get him involved. Better coaching, better offense, etc.
He is a good defender.
His PER is at its highest its ever been with a very low USG rate.
He is shooting 44% on threes this year, which is a career high and may not be sustainable. If you combine last year and this year for a bigger sample size he is at 38% on threes.
Per 36 minutes he is averaging 14.3 points, 8 boards, 1.8 assists and almost 1 steal. So he is a pretty good rebounder for his position as well (and those numbers look so much better than what Casspi is giving us).
I think he just went to a bad spot. The Hawks have played ISO Joe for years. With a better coach and a PG who would get him good looks I think Marvin still has some upside that has yet to be tapped.