Donna's character arc.

What is going on with Donna? I know that her purpose is mostly that of a comic relief at times, but the show has shown that she can be utilised in a more serious angle. When Harvey was fighting for her in court, when she was fired by Jessica, when she left Harvey for Louis. But this episode showed that when they don't have much for her to do, they really don't have much for her to do. The whole angle of her and Benjamin working on a device that acts like her was pure garbage. I know that she isn't always going to have overly interesting storylines. But surely they can do better than that? She's probably the most hot and cold character on the show. Sometimes she's a central character, at other times she really is just there to make an appearance, when it would arguable be better if she didn't.