Yeah I find most of them being basic evil and not pure sense. Shadow Queen and the Shroob are the closes to it though. Most of the Mario villain are just fun and feel they have their own goals and ideals. I don't know enough of Shadow Queen to know for sure and the Shoobs are just surviving being a more parasitic species they really don't know any better (as far as I can tell).
They were good, but Fawful did grow bitter towards the end since his efforts were going unnoticed. They also lacked the closeness of Bleck's group (minus Dimentio) and even the closeness of Midbus and Fawful, which is often not brought up, but they were pretty tight.
He had but the guy cared more for his ego than the whole team-up
If Tas come back, i dighly doubt that after that he will choose to have an assistant but if he do, i think it will be a Boss-salaryman relation (with Tas having an anti-backstabing plan in case)