My team as of now. I like Sableye, but I'm more than willing to change him out for a better lead/other pokemon. Any pokemon is fair game in being removed to be honest. Any help is greatly appreciated. Also disregard the names lol.
Hepatitis B (Sableye) @ Leftovers
EVs: 252 HP / 252 Def / 4 SpD
- Confuse Ray
Mega Sableye should be used over regular Sableye because the former has Magic Bounce to keep hazards and other status moves at bay to alleviate the lack of Prankster. Your current Sableye set is also massive Taunt bait vs. Thundurus. Calm Mind Mega Sableye also acts as a neat win condition if you can get Fairies out of the way:
-Dark Pulse/Snarl/Shadow Ball
EVs: 252 HP/252 Def/4 SDef
Sylveon should be physically defensive to take advantage of its Fighting, Dark and Bug resistances. The EV spread should be 252 HP/220 Def/36 SDef. This is because Sylveon's low Defense comprises its ability to take these attacks comfortably without investment.
What's the point of a Quiet nature on Heatran? Heatran can opt for a speedier support set to support the team quicker, or go specially defensive, as it's done in the past 2 generations:
EVs: 248 HP/8 SAtk/252 Spe
Item: Leftovers/Air Balloon
What purpose does Conkeldurr's EV spread accomplish? Conkeldurr's physical bulk is still good, so you should focus on its middling special bulk to make the most out of Assault Vest: 252 Atk/236 SDef/20 Spe is the spread.