Yeah, it is also important to stress that Ballard had to do a lot in a short time. He was hired late, had to make a lot of decisions about which players to cut, and the quickly patch things up in FA. You're not meant to rebuild a team with FA (and this is not the long term goal with this FA class), but defense definitely looks better now than in December.
What I like the most, however, is that you get a feeling that Ballard has a vision for building a defense, with Grigson it was kinda random. I couldn't see the overall vision anyway, LOL.