I know you meant Decoy, but NACH has the same problem (which I forgot about, oops). But even then Plascrete won't help against Psychographics, which could lose you the game anyway.
Perhaps Magnum Opus, once out, is the best overall way to deal with tags. It protects from SEA, Punitives, and Midseasons, and lessens the impact of Closed Accounts. And unlike other methods of dealing with tags, it's great against (almost) anyone.
Y'know, MO really does seem like the best bet now that I think about it. Plas doesn't help against CA or Midseasons --> Psychographics, NACH doesn't help against any Midseasons or Punitives and doesn't allow the same aggression as Plas, Decoy loses to Midseasons, Punitives, and Breaking News, but allows more aggression than NACH... only MO beats all of these, and is great in general to boot.
Obviously MO has its own downsides. I think it's good there's no universally perfect method of beating tags. If there was, there would be no reason to use anything else.
In sum, if one wants aggression, there's Plas and Decoy, which each have their own merits and drawbacks. If one wants an influence-free, less aggressive version of Decoy which also deals with Breaking News, then there's NACH. If one wants a way to deal with all tags at the cost of having to go with a phase 3 deck, then there's Magnum Opus.