RE: Which Deck Reply Fast!
I would go for Mightyena, since it's so fast. But you should run 4 copies of Blower+. Otherwise it's no use even having it there.
Rhycatty is also an option, since it seems like such a beast. But - as previously stated, if Kingdra is big in your metagame, go Mightyena.
//Hana~
EDIT: Which Dialga PT are you using?