There is SOME sampling bias, but only those in top world guilds completely abandoned frost in favor of unholy, and some of those guilds keep private logs anyway. Bottom line is that there are plenty of highly skilled players skill playing frost (no where near the drop off between fury and arms). Ive consistently ranked (10man heroic) higher than many of my guild mates and yet usually end up the lowest DPS in the raid (vs lock, mage, spriest, rogue, elemental and hunter). And again this is the first tier since T11 where I have had this problem. GC likes to ignore issues involving scaling, but it is very obvious that frost does scale abysmally with everything except weapon damage.