I've been using this Volt-Turn core so far:
Thundurus-T (M) @ Choice Scarf Trait: Volt Absorb
EVs: 4 HP / 252 SAtk / 252 Spd
Timid Nature (+Spd, -Atk)
- Volt Switch
- Thunderbolt
- Hidden Power [Ice]
- Focus Blast
Infernape (M) @ Life Orb Trait: Blaze
EVs: 252 Atk / 4 SAtk / 252 Spd
Naive Nature (+Spd, -SDef)
- Overheat
- Close Combat
- U-turn
- Stone Edge/Mach Punch
It's pretty amazing. They are both frail, but cover their weakness rather well, when the attacks are unSTABbed and/or weak. Infernape takes the Ice-type attacks that Thundurus dislikes, while Thundurus takes Ground and Flying-type attacks, while at same time destroying the Water-types that Infernape cannot touch. Regardless, this is an offensive core, not a defensive core created to cover each other's weakness.
I tried to use Thundurus with Superpower, but I found that Superpower was too weak even against it's main targets: the pink blobs. So, I dropped it in favor of Focus Blast, and left this work of destroying the pink blobs to Infernape. Volt Switch completes the VoltTurn core and Thunderbolt is another Electric-type attack that is more powerful and doesn't force Thundurus to switch. Hidden Power Ice forms a pseudo-BoltBeam combination, while Focus Blast is used against things like Magnezone, Tyranitar and Ferrothorn. It's accuracy is so shitty that I rarely use this move, however; even when I can destroy the target with Focus Blast, sometimes I opt to leave this work to Infernape.
Infernape doesn't receive STAB on U-Turn, but it's versatility compensate for this. Overheat is an attack that hits ridiculously hard even Hippowdon, and has amazing synergy with U-Turn, as after the SpA drop, I can just U-Turn and reset the drops. Also, I don't even need to switch after the drop since Infernape has 3 other attacks that are physical, so aren't affected by the SpA drop. Close Combat is it's most powerful and consistent attack, Stone Edge destroy Flying-types that think that they can deal with Infernape, and opposing Fire-types that could wall Infernape. Mach Punch can also be used because of priority, but I prefer to use Stone Edge so Infernape can deal itself with Flying-types instead of leaving this to Thundurus.
This core is just amazing and effective. Infernape takes what Thundurus cannot take and vice-versa. I was able to counter the Ammongus-Slowbro core very well; I simply try to avoid Spore, then roast Ammongus with Overheat, and when Slowbro comes, I U-Turn on Slowbro and switch to Thundurus, wich zaps Slowbro with Thunderbolt or Volt Switch. This is an hypothetical situation, of course, as a team is not only made of a core. Regardless, the very few other threats that this duo cannot take well, the rest of my team can take, but this is not Rate my Team, so I am just showing my version of the Volt-Turn core.