Stop looking at sack numbers. Williams is a fundamentally sound player in every aspect of his position, who can flash his athleticism, when the situation calls for it. He is one of the best in the game and a key part of why Houston was so good last season. Put him next to Dareus next year and you have the foundations of a great defense. If Kyle Williams returns to form, there is another block, and next to those three, I think Kelsay would be VERY good.
If we could find a linebacker with one of our top two picks, I'd say we could have a dominant defense. With the effect he would have on the overall defense in elevating people, it would be worth it- and more.