VoltTurn leads like Genesect and Rotom are indeed easy to predict but Genesect in particular is pretty hard to counter because of its versatility and unpredictability. I always assume Special Scarf but sometimes there are people who run Physical Scarf or even Physical Band variants. I do think Genesect will be suspected soon along with the former 5th Gen Ubers so VoltTurn will eventually have to find new cores. In the meantime, any tips on how to counter Genesect?
Heatran is pretty reliable, and if you're really having issues with it then Rotom-H resists everything Genesect can throw at it except Extremespeed the extremely rare Douse Drive Techno Blast.