While I dislike stall as a playstyle I have to say that I'm glad that you made this team as it proves that even into such an offensive metagame, defensive strategies are perfectly viable. Other than SD Virizion, which, indeed, could be troublesome for this team, I see a pretty huge weakness to the Magnezone+CB Haxorus\Dragonite combo. Sub-charge Zone can easily set up on Ferro e proceed to kill at least two members of your team, opening the door for a Haxorus\Dnite sweep. Looking at your team, I believe that you could easily replace power whip with bulldoze on your Ferro. You don't really have troubles with bulky waters since Politoed, Quag and even Dnite can deal with them or force them out and this change would only make you slightly weaker to Gyarados. Great team, not much else to say.