Looking at the point scored and allowed per 100 possessions from each game, we can see that Atlanta's best defensive results of the season have been concentrated in the last 16 games:
Here's the game-by-game season average efficiency graph for the Hawks this season which shows both the team's improving defensive efficiency and the team's declining offensive efficiency:
Sine I've done the work, here's a graph of the team's offensive possessions from each game:
And the game-by-game season average of offensive possessions:
The Hawks are again 27th in the league in pace this season.