When were the Super Stunners added to the Freakshow? I don't remember them.
I can deal with mobs that pose particular problems like Sappers, Surgeons, Super Stunners, Paragon Protectors, and the like. Most of them just suggest strategies, and if you're teamed the biggest problem is getting enough in between time to con for them. I generally have targeting macros for them set up and do the obvious things: ranged DPS for the Stunners, take the Surgeon and Sapper out first, hard control and burst damage for the Protectors.
Annoying mobs like Carnies, Seers, late-game Tsoo, and whatever those things in Night Ward are, overpowered because every last one of them gets too much stacking debuff. If your job is to take the alpha and attract the aggro, you may as well just get up and make a sandwich while the rest of the team takes care of them. Mobs just shouldn't have Fear or Confuse, and those Succubi need to stay on redside where they belong. I don't know what interesting stories might be in Night Ward, because I won't set foot there.
But the mobs I actively dislike are the ones that are overused. Council in the 20-30 range get 3 1/4 task forces (Citadel, Moonfire, Hess, 1//4 of Penny Yin). Of course, fighting Nazis is always a mainstay, but still. But even those don't get nearly as old as Arachnos and Longbow, IDF, Neuron Clockwork, and the rest of the rather monotonous late-added content. There probably isn't a single task that's less fun in the game than the Mother of Mercy trial. Even the people who do multiple runs of incarnate trials avoid that one, with good reason.