There really isn't a good way to counter it other than rolling full teams of assassins or marksman snipers. Carnage marauders get a 25% AOE reduction as well. One smash monkey is a nuisance. Two can be deadly if played right. Three or more is just good ol' fashion face roll to victory. This is coming from someone who plays Rage Jug as a main. Just pick a healer and sit on him for 15 minutes.
I just can't help lol'ing at the irony. One of the reasons BW nerfed adrenals in WZs was because of the sick burst some professions were capable of achieving. Now we're back to 7k smashes sans adrenals. Part of the reasoning for tweaking rage this last time, from my understanding, was to give quality of life improvements and to make Rage viable in PvE. Clearly BW did not give much forethought towards PvP when they implemented these changes.
That is kind of sad. Use to be where it was more of a hazard to derpsweep, since it had quite a bit of skill lag and was very niche'y. In PUG's I can see this as a huge problem (Which is what I have encountered as well in some of the 10-49 bracket, usually see between 3-4 on either team) and less a issue in Premades. (Though still a issue.)
I doubt BW will address it though very quickly.