Originally Posted by Shimboo
It's too challenging to be a regular gym, that's probably why you only encounter a dark type trainer in the elite four.
Dark types, hard? LOL, they would set it up to where you could catch wild pokemon that are good against Dark types, since they're weak against Bug
moves, you would look for those types (Heracross
FTW!) or have those type of moves on your pokemon to counter those dark types in said gym.