NtK,
If there are any of these players in our area I don't know of them. Not that I am at too many events, but I don't even hear stories on Ordo of "That douche I played the other day..."
Maybe I missed it, but the elusive player that does this may or may not be Bigfoot. Or maybe it is that Ordo is the cool community and there is a shadow community of dicks out there...
Anyway, the only place I have seen the tactic is on the interwebz... and more people worrying about it than people suggesting it as a valid tactic.
Now if facing one... Engage to the front with an armor killer (that gives you about 6 models attacking to his 2), or kill the unit with shooting/spells, flank charge it with something nasty (remember he'll have no supporting attacks )... how about a cannon ball?
Anyway, we all know the rest of the army (and yours) will matter on how you can deal with it, but there are certainly ways, and as others say, "Junk Punch" is the best.