Well, the Elite 4's types are Ghost, Fighting, Dark, and Psychic. On the one hand, you have at least one pokemon that resists moves of each of those typse. On the other hand, while you have two pokemon likely to know moves strong against Ghost-types or Psychic-types and at least one likely to know moves strong against Fighting-types, you don't have anything that'll be the same type as moves that are strong against Dark-types (so they won't get the same-type attack bonus from those moves).

Aside from that, BW is designed so that you really can beat the gym leaders and the E4 with your favorites - you don't, strictly, need type advantage, and if you have fun with those six, have fun with them!