From my looking at Pokebattler:
I always sort by time to win, but noticed the power (TDO basically) was also higher for the faster killers generally.
In neutral weather, dragons were the best. It flipped between Ray and Palkia, and even Salamence, depending on moves. Also recommended Draco Meteor on Dragonite. I'm guessing they can all survive a dragon charge attack.
In windy weather, dragons obviously still reign supreme then.
In foggy weather, Gengar does the best DPS. Ray is second, and Mewtwo is third.
In snow, Mamoswine comes first place. Weavile is second.
However in anything other than snow, Weavile performs better than Mamoswine (often 7th and 8th, or 8th and 9th overall). Weavile not only does more DPS, but also has higher power (due to his Psychic immunity-tier resistance) - except against Thunder Mamoswine is better for both DPS and TDO (due to his own immunity-tier resistance). The reason for this is that dark is also super effective, so Weavile takes Feint Attack instead of Ice Shard as his fast move and gets more damage from it.
So, a full dragon team will still treat you well. Always top-end attackers. Only alternatives that you'd potentially want are Gengar/Mewtwo in fog, or Mamoswine/Weavile in snow. The former is rare everywhere, but the latter is very possible.
Gengar actually does BETTER against Zen Headbutt sets (I guess because the fast move charges him faster) - but still weaker than Dragons in neutral weather (comes 5th overall).
