I really dont think Gensect Virizion on their own is a very good deck. They lose almost instantly to fire types. Mainly Victini Ex with Victory Piece. With the plasma badges, you have a weakness to the drifblims. Safeguard pokemon as well as mirrors would require you to have a G booster. The Trubbish deck would give you a lot of trouble. Turn 2 it can be hitting upwards of 100 damage, even more if you put on plasma badges, and it would be simple to move around silver mirror and bangle to cause even more trouble. Though you can G booster them to death, but having to waste 2 energy is just not going to be possible for 6 knock outs.
A blastoise deck could also give you some trouble if they manage to set up. Black Kyurem ex can do 200 damage consecutively with ease with blastoise and superior energy retrieval. While Genesect requires a lot of energy, and G booster to do the same.
I would suggest a few things. maybe plasma frigate to negate the weakness to fire. Tropius is a good grass pokemon. It can help set up early turns with return if you lack tropical beach. it can also murder the water pokemon in blastoise decks and only be a 1 prize attacker. I find tropius so good that if i have an open pokemon slot in a deck that runs some form of grass energy, its almost always the first pokemon that goes in.
You could also try a 2-2 Abomasnow since it does 80 and confuses and is also a water type that isnt an Ex or Plasma. It can greatly help against safeguard, silver mirror. You may think, why would i bother charging up this pokemon when it costs the same energy for genesect ex? Simply because of its typing, fact that it does not give up 2 prizes, and can hit through safeguard and silver mirror, and it can also help with confusing pokemon. It can also add silver bangle for 110 damage total, making 2HKOs on most Exs.
I havent really read the older posts. But why Mr Mime. It doesnt really help since both pokemon have high HP totals, it seems like a waste of space and possibly a starting pokemon that is just utterly terrible.