Uh, no one said other Gliscor sets weren't competitive. But since you mentioned it, AcroBat Gliscor attributes a lot of its success to the ability to set up via Sand Veil hax, which technically makes it less competitive than a set that doesn't rely on hax to get the best results, like SubProtect. And in a fast paced metagame with things like Celebi, Dragonite, Gengar, Gliscor, Gyarados, Jellicent, Landorus, Latios, Latias, Reuniclus, Salamence, Starmie, Tentacruel, Tornadus, and Venusaur running around everywhere in OU, spamming Close Combat is not always a good idea. At all.
Besides, most of the stuff you mentioned isn't even bad. Maybe Terrakion...sometimes...but some of that other stuff? Prankster Sableye is useful at times, but it's pretty frail and fails to really do anything to Pokemon that don't mind a Will-O-Wisp (special attackers, Fire types, Magic Guard/Magic Bounce Pokemon, etc.). SubProtect Gliscor is mainly useful for getting past its usual counters. If it PP stalls some random sweeper, then that's just a bonus. Besides, since it's running Earthquake and Toxic alongside SubProtect, it's walled terribly by Skarmory, Bronzong, any Steel type with a Balloon, and really anything that can take an uninvested Earthquake and knows Taunt. Headbutt Jirachi is just terrible. HydraRest Vaporeon with Roar is hardly a team-sweeping threat. It's just annoying is all. CM Slowbro is always going to have some kind of coverage issues, and it's still going to have problems with Pokemon like Gengar, Jolteon, Magnezone, Breloom, and Rotom-W. Perish Song is useful against Baton Pass teams and as a last-minute resort against Reuniclus on stall teams, and that's about it. Sub Breloom is just another Breloom set. It still has several sturdy counters in OU, plenty to pick from if you really have a problem with it that badly. And that Chandy + Durant combo is a gimmick at best, and it isn't even legal outside of Dream World. But hey, since you seem so upset about the lack of prediction, let's just throw every blasted set that uses Substitute or Protect to ease prediction under the bus too.
And on top of that, people who use those things have a "problem"? No, just...no.