I think the Battle Master Fighter needs a bit more, let’s add some via a feat.
Battle Mastery
You are the god of war knowing how to make any weapon do what you want them to. Gain the following benefits:
- Double your proficiency bonus applied to your Maneuver Save DC.
- When you gain an extra superiority die at level 7 and 15, gain two instead.
Thoughts?
Throat Punch Games 
The Battle master is interesting because he’s setting up his companions for pulling off something awesome. One of my players figured this out when he was trying to do awesome stuff on his own to be the super cool fighter, but actually ended up creating situations for the monk to pull off amazing feats of hack and slash.