It's been a while, but why shouldn't I try this.
Landorus-T is good overall. If you need recovery more than contact damage, run leftovers instead. Use Landorus to bait Pokemon that are weak to Choice Koko, like Zapdos and Toxapex. The only problem you may have from this is that your team is pretty weak to Ice. You might want to change Landorus out for Heatran if you find that is the case. If so, use this set:
Heatran @ Leftovers
Ability: Flash Fire
EVs: 248 HP / 132 SpD / 128 Spe
- Magma Storm/Lava Plume
- Stealth Rock
This passive Heatran should help as a Rocks setter. Toxic can help punish the bulky water types that switch into Heatran. Will-O-Wisp shuts down Physical threats like Mega Mawile. Magma Storm can help trap and residually damage some threats like Toxapex. Lava Plume is better for accuracy and has a high Burn chance, which works in better with Toxic.
Don't use Mega Beedrill. Mega Beedrill isn't viable in OU. At all. :P
I suggest Mega Pinsir as a replacement. It is a fast, physical sweeper, like Mega Beedrill, but has Aerilate to do massive damage. The only thing you can't do is Pursuit trap, but that's fine here. Run this set:
Pinsir @ Pinsirite
Ability: Hyper Cutter
EVs: 252 Atk / 4 Def / 252 Spe
- Swords Dance
- Earthquake/Close Combat
- Quick Attack
Hyper Cutter prevents Pinsir from getting intimidated before it mega evolves. Earthquake is generally fine, but Close Combat hits things like Celesteela better.
This is a fine Tapu Koko. Most sets run Thunderbolt instead of Grass Knot, but you don't need to run Thunderbolt. Just some usage tips: Try to send Koko out against common Protect users, as using the same move twice makes sense and doesn't reveal that Koko is holding the Choice Specs. Use Volt Switch to wear Grass types down.
Tornadus isn't run Physically as much as Specially/Split, if at all. Most hold Rocky Helmet/Flynium Z and have Defog, not Taunt. I see that you want Taunt to stall break/prevent set-up; as well as having Rotom Defog, so Taunt is perfectly fine. Physical investment isn't needed as much because Superpower already OHKO's Chancey and pokemon that are weak to Superpower) at 40 atk (Neutral Nature), and U-Turn is to pivot.
If you want to run it physically, replace Hurricane with Knock Off (since Hurricane will be quite useless) and put 4 EV's in Defense. Use Rocky Helmet/Fightinium Z, or Life Orb.
If you want special investment, use this set:
Tornadus-Therian @ Rocky Helmet/Flynium Z
EVs: 252 HP / 4 Def / 252 Spe
- Knock Off
With special investment, even Pokemon like Magearna and Tapu Koko are worn down. Knock Off is great for shutting down a lot of Pokemon that rely on their items for Damage, Defense, or Recovery. U-Turn allows Tornadus to pivot, and threatens Dark types like Mega Tyranitar. Superpower with this spread:
40 Atk / 216 SpA / 252 Spe (Naive) allows Tornadus to OHKO Chansey and Stakataka, as well as common Stealth Rock setters.
Toxapex is also okay. Use Toxic if you find it too hard to sustain them applicably. This EV spread is better:
248 HP / 196 Def / 64 SpD (Bold). Keep Toxapex healthier (via Recover or Regenerator pivoting) as it does its job better the healthier it is. Switch it out into walls to scald burn and or get a layer or two of Toxic Spikes.
Your Rotom-W set is interesting; It doesn't need Modest, Bold would be much better. Use this one of these spreads:
248 HP / 204 Def / 56 Spe (Bold) OR
248 HP / 124 Def / 80 SpD / 56 Spe (Bold). 56 speed allows Rotom to out-speed Choice Band Tyranitar. The 80 SpD set allows Rotom to tank special attacks from Pokemon like Choice Scarf Blacephalon, and then OHKO them with Hydro Pump. Pokemon that can't harm Rotom well are the best to send it out into (usually to defog). Such Pokemon are Heatran, Mega Scizor, and Protean Greninja.
You don't really know how well a team can be until you try it, so go out there and show 'em what you're made of!
Hope I Helped!