Hey Guys, Bills fan living in Houston here. Wade's defense did not perform well in 2013 despite having quite a bit of talent. There has been a relative consensus down here about some of the things that went wrong.
The pass rush under-performed: as you know, in a 3-4 most of the pass rush should be coming from the outside linebackers. Despite investing high draft picks at the position, and JJ Watt taking up extra blockers, the Texans did not get much production out of them. The Texans finished 29th in sacks in 2013 with 32, 10.5 of those coming from JJ. Without Watt making miracles happen at the 3-4 Defensive End position, production would have been much worse.
Wade mishandled the Ed Reed situation: No question that Reed was a bad free agent acquisition given the money the Texans paid him and his declining speed. However, part of the value of the signing was supposed to be the insights he could bring to the team as one of the best safeties to ever play the game. Reed didn't get as much playing time as he wanted, which was fine given his limitations. But it seemed that what frustrated him enough to make sure he got released in November is that Wade was not taking his suggestions into consideration despite the Texan's defensive struggles. Seemed that Wade was too set in his ways to take any input from Reed.
Lazy Schemes: The #1 beef in Houston with the entire Gary Kubiak/Wade Phillips regime was predictability. The Texans still had most of the talent that got them to a 12-4 in 2012, but other teams simply got wise to the same predictable schemes from Gary and Wade that would not be adjusted within game, or even from one game to another. Notice how Belichick is willing to change his entire game plan from week to week, and how much that factored into the Patriots 2013 successes. The 2013 Texans were on the very opposite end of the spectrum. The lack of adjustments also goes a long way in explaining Wade's career history of making bad defenses good quickly, but then experiencing a large drop off in production instead of making the jump from good to great.
Losing Pettine so soon is a huge blow for the Bills. I hope they can get a DC who will follow in his footsteps rather than looking back to Wade. Just my opinion, for whatever it's worth.