Stego i think NC would be more interesting if there was a mix of clans. But so they are not the best you could add consequences such as you dont learn all the clans moves.
mixed clans is ftl even if its just 2 i know some combos that could easily overpower everyone else with multiple clans and the way it is now is good because theres a little of everything and not all the same thing with mixed they might all go part med or uchiha or something