I find a line up in a gym that has the following in them and more than one slightly annoying to battle against: Vaporeon (WG/AQ), Blissey (ZH/DG), and Snorlax with (ZH/BS).
Dragonite to me isn't a deterrent even with DT/OT nor a bunch of high CP Rhydon's. I encounter them all of the time in gyms. They aren't even difficult to prestige against with something half their CP.
The above three tend to me more tanky and spam their charge moves more often. Your dodging game with them has to be on point.