If there's any good Seniors there with average luck then Gengar will not win Seniors. It's so easy to play around it. SPs will get rid of Queen via Bright Look or Time Crystal. Dark Flygon/GGW have the Weakness edge and can pwn you with Uxie. Beedrill can just attack like mad and guard the goodies while keeping most trainers out of the hand. Machamp fails to Gengar, but Machamp just fails in general. Gengar can win by sheer numbers but that's it. It's got SICK lines (Gastly Pitch Dark, Haunter can have free retreat or Hoodwink 3 Supporters to set up a Poltergiest. And Gengar is just soo good if you force flips and get it out fast enough they can't Unown G the Baltoy. Either Looker them in and force them to draw 1 or 2 cards or Poltergiest a hand of a lot of trainers. However, all of those can notably be stopped. I'm going to go out of a limb here and say SPs will take 2/3 divisions or all of them. Running only basics is consistent and they have so many tricks they can use. I'd say a Palkia lock will win Masters/Juniors and something with Luxray will take the other. But anything can happen in Juniors lol.