This looks not bad! Volt Switch variants of Raging Bolt are going to be a big issue for you, though. Certain Gouging Fire sets will be trouble, but you always have Darkrai Trick Scarf for those. Probably my #1 concern here is Zamazenta, if they Tera Steel, Darkrai is your only out. Consider Tera Ghost / Fairy on Heatran to help with this.