I know I don't post around here much but hopefully my opinion is still valid!
I honestly have not had any problem with Stockpilers. I played against a couple and did fine. Of course, it might be partly because I have Encore Fidgit, Leech Seed Celebi, Zen Headbutt Jirachi, and also a Haze Tentacruel at one point. I had my own Arghonaut as well but that doesn't really do anything to stop theirs (I don't use Thunderpunch) besides being Unaware.
If you have like 1 or 2 of those on your team, which you probably would anyway (also Revenankh works), I don't think you would have any problem with Stockpile Arghonaut. I haven't had too much of a problem against any of them actually unless I'm like down to Celebi and Fidgit and both are at 30% or so but then obviously I could lose to anything.