I agree that a smaller cast works better. Voyager would have been better if the central cast was Janeway, Chakotay, Tuvok, Paris and the Doctor with Kes, Kim, Torres and Neelix as secondaries. ENT half-tried this with the Archer/Trip/T'Pol thing but didn't try hard enough.
Smaller Central casts with larger Secondaries is the better formula.
Smaller Central casts with larger Secondaries is the better formula.