I don't see why you need all of that SpA on this set. You say it's to OHKO Gyarados after a CM with Stealth Rock up. My question is, who cares? With max HP, Gyarados still isn't going to do shit to Suicune, so why do you need to OHKO?
You can change the spread to 252 HP / 40 SpA / 216 Speed and make Substitute a VERY viable option. Right now you lose to Blissey 1v1. You win with Subsitute, it's that easy. Substitute essentially blocks "hax", since now if you get into a CM war, you can't be criticalled either. You don't need as much SpA because you're boosting it with Calm Mind. HP Electric or Ice Beam can easily be dropped for Substitute.