This most recent shot is a bit off. Perhaps the color is just a big muted, but the lower flash is better. A diffuser is a really good idea.
I do a lot of cosplay photography and just got booked to shoot MechaCon in NOLA later this summer as well as some private shoots in the early morning. I am also doing a group shoot with 3 other photographers this Saturday. Cosplay photographers also rarely charge, and are often photographers outside of that subject matter that do charge. Cosplayers are really lucky like that!