I've been looking at van's recently and can't help but notice that the most rust prone of all the types I've looked at appears to be the Mercedes Sprinter? Year for year, Transits, LDV's, etc have far less serious rust on them which I can't quite get my head around because I've always perceived Mercedes as being a quality product. So, why do Sprinter's rust so badly?
Mercedes went through a period of serious quality control issues and many chauffeurs switched to other makes as a result.
Perhaps the vans were also affected and the ones you have seen date from that period?
Yes I've heard that too shoota, I believe it went downhill in 1994 and they didn't sort it until 2008 so any Merc built within that period is to be avoided at all costs.
As Jeremy Clarkson said of his own SL, it goes in to the dealer to be fixed and comes out more broken, that's par for the course of Mercedes ownership.