Replace Ice Beam on Suicune with Sleep Talk, and change the nature to Bold and EV spread to 252 HP/248 Def/8 SpD. Trust me, it works a lot better, he's a setup sweeper/staller;56 SpA EVs aren't going to do much for you, and your raising your SpD with Calm Mind anyways. Volt Switch over U-Turn on Tapu Koko because your set is running Special Koko so a physical move isn't a great idea. I know U-Turn is probably there for Ground Types, but HP Ice usually OHKOs most Ground Types anyways, especially pokemon like Garchomp, that are 4x weak to ice. Change the EV spread on Koko to 252 Spe/252 SpA/4 SpD and make his nature Timid. First of all, your missing 4 EVs on him, second of all, your not taking advantage of his great speed, and with your current EVs he'll get outsped by common Ground Threats in OU like Garchomp and Zygarde. Also, replace Wild Charge with Thunderbolt, and remove Fairium Z for one of these two: I prefer Choice Specs on Tapu Koko because of that STAB Electric Terrain Choice Specs boosted Volt Switch, but if you really need a Z-Move user, than give it Electrium Z. Replace Defog on Gliscor with Facade or Roost; you'd be suprised at how bad of a Defof user he is. Trust me, I've tried, and it never works. I think your Heatran doesn't contribute much to your team; generally people run him on teams to abuse his Flash Fire ability because their other pokemon are weak to fire, but you only have Weavile for a pokemon weak to Fire. I would suggest replacing him with Ferrothorn, and if your opponent switches into a Fire Type, you switch into Suicune. Also tbh most of your team isn't very competitively viable. (Half your team isn't OU!) I'm not going to suggest you remove half your team, but I don't think your team will do very well as is because of this. Anyways, have a good day and if you need OU sample teams to use for reference, search up OU sample teams 2018 January.