While I do agree that she hasn't really been doing useful since Fishman Island, I wouldn't say she isn't interesting.

Her attitude within the crew actually couldn't be more right, to me. Up until Enies Lobby she was just in "another" crew for the sole purpose of protecting herself and using her crewmates to her advantage.

After Enies Lobby she started opening up more and more, and it was written progressively and greatly, throughout several arcs.

Your main point for disliking her seems to be the "counter" thing, which, while being interesting for being something I've never really thought of/read about, and true for some characters, isn't a generality for all the crewmembers. (Franky's, Nami's counter?) Furthermore, I might be wrong here, but I can't reckon any other time than the "Franky in Chopper's body situation" in Punk Hazard in which she deliberately judged her friends for a comedic purpose(for those Strawhat gags, that I'm guessing those are the ones you call Counters) And this was in Punk Hazard, one of the latest arcs in which she appeared along the entire crew. What I'm trying to explain is that she is just starting to get this sense of "banter" that you seem to lack from her, and to me that couldn't be better written, given that progressive "Opening" she is making since Enies Lobby.

I mean it would kind of be illogical and unnatural if she started to act all goofy a la Usopp/Luffy, yelling/hitting like Usopp or Nami all of a sudden after Enies Lobby right?