The two trainers in GameFreak building only use Pokemon which give HP and Speed EVs (And they give good numbers too)
http://pkmn.net/?action=content&page=viewpage&id=8914
I heard some of the breeders that always approach you for rematches only have Pokemon that give out certain EVs.
As for the VS Seeker, I don't think it's in B/W2. And it doesn't work the way it used to if it is.
EV training is pretty easy though, you have all the wings (Health Wing etc.) which give one EV each. There are all the trainers you can beat daily in the two sports domes. In Join Avenue you can use the Dojo/other services to stack on EVs. You get given power items early in the game and BP is easy to get this time around.