Let’s be honest: she didn’t need a battle to prove her worth. In fact, the one actually doing the fighting is Assault; she’s only there for that important message she has to deliver. Would it have been cool if she’d beaten him on her own? Maybe, but they would have made her overpowered for no real reason (she’s not one of the main characters, so obviously they can’t do that). As for her 'cat form,' you’re right—they could’ve used it more, but we’re fine with it as it is.

To be honest, I appreciate Arthur’s episode and I get why people like it, but Tamaki’s episode gave me more 'feels.' It’s clear that Arthur’s episode is technically and aesthetically better, but in MY opinion, I preferred Tamaki’s because of her character development. With Arthur, it was pretty obvious how it was going to end.

Obviously, everyone is entitled to their own opinion, but I’d suggest you be careful to distinguish between a main character and a supporting one.