It most definitely is. And an uninformed one at that. This defense is built predominantly by Nix who added Mario, Dareus, Gilmore, AW and Bradham. Should also have been Kiko if not for the trade. Kyle and Leo are holdovers from Levy. Whaley has added Hughes and Brown, along with placeholders at the third LB position and free safety.
On the offense, there are only two competent linemen (Glenn and Wood) and neither is from Whaley. They paid an arm and a leg for a star receiver with no QB to get him the ball. Woods was a Nix guy. Fred was a Levy guy. The rest of the offense sucked. Including all three of the linemen Whaley drafted last year.
As for the offense being "the most improved in the league", we'll have to see that once the season starts. It can be argued that they overpaid for all three of their big additions in Clay, McCoy and Harvin. Their biggest two issues on the team were QB and oline, and Cassell and Incognito are not going to fix that.
He gets an A for spending a lot of fracking money like a teenager with Daddy's credit card and possibly hurting our cap situation a few years down the road. But as for results, he's a C- to D+ at best.