Since when running Sleep Talk on some Pokemon doesn't show how unhealthy a Pokemon is ?
You have to trade a useful move (Healing Wish / Trick) solely to be able to deal with one Pokemon ?
One of the points which were put forward for Azumarill was the fact that people have to run Shed Shell on Alomomola to deal with it. It's exactly the same if people have to run Safety Goggles or Sleep Talk on their Pokemon.
I definitively disagree with all that have being said. It's not that easy to pressure Breloom since all the Pokemon that can pressure it can't switch on it if you have not scout its moveset. Yeah you have to do 5 hit with LO Bullet Seed to OHKO Gliscor but that also mean Gliscor can't come more than 2/3 times on Breloom (and if you Roost and Breloom stay and Bullet Seed then Gliscor is gone).
Is Scizor unhealthy because people have run Babiri Togekiss and Sylveon with fire coverage to catch it?
Is Latias unhealthy because of how much more common it made Pursuit?
Mane's making it a neccessity to run a Ground type?
What about Suicune placing massive constraints on teambuilding simply due to existing and forcing every team to run either a Grass that beats, Trick, Haze, or Roar?
The top threats are threats for reason. They're going to warp the metagame as people try to innovate to stop them. Breloom has shown it is a top threat, and as such people are trying to stop it. Hogg summed up my thoughts pretty well about having no true defensive counterplay isn't a reason to ban something. Azumarill was able to pressure the metagame to an insane degree with one set. This is something Breloom is not nearly as capable of. Fliers can deal with non Rock Tomb, Ghosts come in on Poison Heal easily, and any Mach resist revenges it. Breloom itself can't switch in on anything barring the most passive bulky waters and walls. I don't think the argument of people trying to stop it more easily makes sense here (or to compare it to azumarill.)