Kamala worked as a one-shot character. Part of what made her so fascinating was that her time to be a unique person was limited before she was destined to basically be sold into slavery to be someone's toy. She couldn't have worked as a weekly character. What would she do? Change into a different person every week? It would make DS9 like Dollhouse. As for Famke as Dax, I like this actress a lot (X2 is my favourite superhero movie and she's a big reason why), but I haven't seen anything in her work that shows she'd be able to play Dax with as much charm as Terry. I don't think she's a bad actress, I'm just used to seeing her play more serious characters. I know she's done comedy, but I haven't seen it, so I can't see her bringing the same free-spirited energy and breezy confidence in her performance in the role that Terry brought.