Platinumdude covered a lot, Rotom-W should be changed to the "Standard defensive set", and SR can definitely help the team. I think your best options right now would be a heatran or landorus-t, which serve the dual purpose of beating Charizard-X, which is threatening to the team. Some carry Earthquake though so you might want another check to mega charizard x, maybe dragon dance mega tyranitar as a sweeper since you don't have a mega yet and it could help your team's offensive capabilities. Keldeo could be a good check as well that can give your team some offense. If some of these are hard to find in game, just make sure you have charizard-x beaten, also Aegislash looks threatening with shadow ball, so a counter/check for him like Bisharp, Mandibuzz, [Mega ttar is a check too], could help out since Aeg is really common in single battles.
paired to kaori & vrai