More dark troop barracks and sooner....
As attack strategies develop, dark troops are being used more and more. Additionally, larger, more complex armies are being brewed for even basic, village raiding. The addition of another AD on TH7 means we now need to look at other attack strategies to successfully three star bases.
All of this increases prep time, the bane of this game. Armies are taking one, two, and three hours to train up. Players are using more dark troops, but we lack adequate barracks to make training times even approach reasonable.
Take TH7, for example. We have just one dark troop barracks and it holds only 50 troop units. To run a hog ride attack, you have to train ten at a time, four times. In other words, you cannot train a single attack at once. The same can be said for other dark troop attacks at later townhalls. Two just isn't enough. (Even the original game starts you out with two regular barracks at TH1.)
We need our second dark troop barracks at TH7 and at least a third (or potentially four) later in the game. This will help reduce training times and improve overall playability.