I emailed Jeremy Hicks on the DRC (and other) issues and he put me in touch with Paul Adcock (Customer Services bod who liases with Audi UK Tech). Paul advised me that Audi are aware of DRC issues with the RS6 and all Audi garages are supposed to order (and fit) a protective boot with all shocks ordered for RS6s now. The boot was available from 20/04/2007. This helps to prevent dirt getting in and breaking the seal (oh er). But it'll also hide the evidence!

Just spoke to Paul again and he said that the dealers were given a software update to their parts ordering system on the 17th July 2007 such that they cannot order a new shock without ordering a boot.
He also told me that the Central Valve can now be repressurised but this requires a tool that should be available in May 2008, part number ASE42501200000. Until then the central valve has to be replaced if it loses pressure.
So if you have had DRC repairs recently and you don't have the boot... then you need to shoot the servicing dealer as they are not doing as they were told.

HTH
Grant