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You guys keep calling them Arceus support cards, but Arceus is the one doing the supporting. Heatran is the one that gets the retreat cost buff, not Arceus. Notice the symbol on both Heatran cards.
In other words, you guys have it backwards. Instead of having just one Arceus deck with support cards in it, it's more likely going to be multiple decks where Arceus can be added for additional synergy.