@Meganium Sulfate: You're right. Posion/Normal is a very bad type. However I have to mention that typing is a defensive mechanic. STAB is another part. Blissey and Bastiodon are good examples for Pokémon who don't profit from their STAB. What would happen if we made a Rock/Fighting type with a bad physical attack stat (both Fighting and Rock mainly include physical moves) or a bad movepool (see Eelektross), so that it cannot profit from its STAB very well. On the other hand Normal/Posion would be easier to balance ... I'm undecided.