i would argue that in many cases, having multiple directors is actually one of the great benefits of television and even within the constraints of a show, they still have considerable freedom to define the tone. tv is also a great format for relative unknowns to find their voice. steven spielberg was an 'unremarkable' tv director until he worked on Columbo and his episode- The Perfect Murder was a breakthrough that still stands apart to this day. similarly, put together any two episodes of the x files and the range is pretty incredible, Grotesque and Jose Chung's From Outer Space are only a few episodes apart and they might as well be entirely different shows.