Most of the time I don't see the point in changing HCs during the season.
In the Cowboys situation, I can see a point in it. (not that it's definitely the right thing to do though)
It's still very early in the season, so a coach has some times to put something in place. Changing a coach at week 12, is generally just a complete waste of time.
The Cowboys have enough talent to win a lot of games. To do that, the team has to be prepared on game day. That is something they haven't been three of the four games they've played. That lands directly on Wade's head. The Cowboys should easily be 4-0 right now. If you continue to leave Wade as the HC you risk the same failure the rest of the season. A change in coaching can add a spark to the team. Especially if it's a no-nonsense head coach.
As I noted, I'm generally against changing HC during the season, but I will say this. I was all for firing Wade long ago. It's early enough in the season that the team can turn this around. The problem is, the team always returns to what it is under Wade. An ill-prepared team. I think a change (to the right HC) would be a good thing now. Now, I mean now. If you wait till week 10, then forget it. Wait till the season is over to switch. If you're going to do it, do it now while there is a lot of football left to be played.