I play the jolteon glaceon mew deck. It is very effective, I don't think there's a particular meta it's weak against. When I lose, my experience is that my opponent plays well timed Lysandres or switch (it takes time to power up the pokemon that are actually on the bench). Xerosic, Delinquent, and the stadium that suppresses abilities... Drawing a blank on it's name.... Also, N, Red Card, and Judge can really hurt as well. So while there is no single deck that I'm afraid of, I'm constantly petrified of N or Delinquent or even Team Flare Grunt. Believe me, from your end of the table it may appear to be an impenetrable fortress but from my side it's a fragile house of cards.