The counter-sue idea doesn't really work for patent troll companies though, which only hold patents for extortion, and don't do any productive work of their own.
This isn't completely correct. It does work if the counter-suit claims are valid and encompassing - sanctions in the legal process can provide significant leverage, especially because the "patent-trolls" are heavily involved with patent attorneys.
"Reback often tells the story of how a team of IBM patent lawyers went to Sun Microsystems Inc. in the 1980s and claimed that the then start-up was infringing on seven of its patents. After Sun engineers explained why they were not infringing, the IBM lawyers responded that with 10,000 patents, they would be sure to find some infringement somewhere." -- The Washington Post
The point is that patent trolls are pure IP companies that don't actually do anything; they can't possibly be infringing one of your patents because they have no products. That's why they're so much worse to deal with than other companies who could be counter-sued for infringement of your patents, or for theft of trade secrets, or for something else similar.
With patent trolls maybe you could counter-sue for tortious interference, but that's a pretty hard one to make stick, or you could get a judgment rendered that requires them to pay your fees if the suit is totally ludicrous, but I'm not sure I've ever heard of that happening in any kind of patent lawsuit.