A bit of an extrapolation to suggest that because I dont buy from GWD I dont buy from a whole heap of other places (because I do buy from many of the places you mention). But GWD has this ability to spruik that I find most unappealing and their track record of selling wine with trophies (from Timbuctoo maybe) which then taste like cough is one I dont like much, and neither do many of the other wine buffs I know. Its an opinion I know but one shared by many that GWD are very misleading, using wrong years to advertise wines and offshore wine shows (if the wines are so great why have they not been submitted to an Australian wine show) being but one example. And in your last sentence it's just possible that Penfolds know a little better than your auction site which wines they make.
You mention Viking, is it just possible you bought the 2011 because GWD sold it as just as good as the 2010? Because that is after all their modus operandi. PS. Yes I do know the wine but no I didnt buy the 2011 because I rely on the advice of others than GWD. And I agree Epiquire is expensive.