As far as Hidden Power go, I ask myself "what is more likely to switch in and wall me? A steel type or a dragon?" Well, to me it feels like steels are a bit more common. Also, seeing how it's a rather steel+dragon-oriented metagame, the use of HP rock feels foolish.
A tweeked sub-seeder:
Serperior
Ability: Overgrow/Contrary
EV: Spe: 252 SpD: 252 Def: 4 or 236 Speed/252 SpDef/20 HP
Item: Leftovers
Substitute
Coil
Leech Seed
Dragon Tail
Dragon Tail as well as Leech Seed benefits from Coil in some way and the SpD is maxed 'caus we attempt to boost defense (right?). Speed is maxed in order to outspeed things (I haven't been doing any cals) and wimsicott can't touch you behind a sub. Dragon Tail anything you can't seed back to their balls.