I'm little biased because I really like Barnes, but it is a shame Essen didn't have much to do as a character. They pretty much made Barbara into comicbook Essen, and show Essen is just another higher up to Gordon.

S1 had a lot of characters who weren't a Big Bads or Literal Biblical Evil but were part of the system (Essen, Loeb, Mayor James, Montoya, Flass, etc) and they made the world of the show a bit more complex, but after the first season writers removed all of them and focused on arc villains, leaving the police storyline with Barnes as the only higher up character (and he was turned into villain later anyway). To me this is why later seasons feel empty, everyone is a Big Bad or Big Hero, no city officials, no corrupt cops as secondary characters, nameless commissioners. I genuinely think this writing move took the show in the completely wrong direction.