Hi Dave, this is my first response to any question so take it with a grain of salt.  The subject, artistes, can be masuline or feminine and when the group is indeterminate, the default is masculine.  The fact that the two examples are feminine has just thrown you off a bit from the general rule.  Anyway,  that is my opinion. 

I agree with your answer Frank, all except for the last bit where you mentioned the 2 examples were females. Maurice the ballet dancer was actually male (or it would have been danseuse, not danseur)