Joe even though I love auf, it went downhill a lot after xwis started, but it isn't even top 10 of all time anyway.
From what I remember, ba and omerta were the top 2 xwis/xcl clans and wol it was a whole different story. They'd be in the top almost every month but then clans like judges/dru1dz/bbw/auf/etc would get rank 1/2 a bit pretty often.
As far as players go, prep is a pretty good judge imo since he's been around for so long. Most of the old pros are long gone, but even if they did play now there are long gaps of perhaps a decade since they played. Tomi imo is the best ever based on sheer rank 1/2 when all the top players played. He would be rank 1 on yr and ra2 in the same month multiple times a year. Perhaps later on he bailed as matt said, but I don't remember him bailing anyone when I played 01-07.
The only issue with prep is he wasn't a top player in 01-03 so I cant image he'd know too many of the early players. You'd really have to play from start to finish as a semi-top player to know. Prep is about as close as it gets so I'd agree with him.