Well i'm training for him right now, and his latter two you're right about - I do plan to use Eurasia against Altaria and Pakistan for Haxorus. For Flygon (that does have Dragon Tail, i'll mention), Singapore resists Earth Power (although that hits her lower Special Defense stat) and he doesn't resist Grass because Ground/Dragon, so I plan to use her for that. With Druddigon, Slovakia can learn Acid Armor, but he has Dragon Tail to say screw you to my attempts at stalling. But here's one problem I have: Slovakia is about to learn Gunk Shot (Level 49), which would be great for her bigger Attack stat...but i'm wondering if it's worth it or not. Not only is Gunk Shot rather impractical with its 70 accuracy and 5 PP (especially in a challenge like this where I have to be mindful of PP), but I don't know what to drop for it. ThunderPunch I want to keep because i'd rather not drop a Move Tutor move, and it'd help for Marlon's Gym after. Acid Armor I like just because, Sludge Bomb is there to have extra PP, and Rest is good for restoring health.
That said, if all goes well, I should get to battling Drayden today, if not definitely tomorrow.