Just looking through the rules and settings page there is no indication of certain classes having to play certain races. Also using google I can't find anything either other than some lackluster forum talking about how a team couldn't play trolls so they lost. Even the commentators yesterday mentioned their surprise that not many people where playing human. I think its just the 264 Medallion has enough Resil on it allowing you to stack more PvE gear + The fact that stoneform, escape artist, shadowmeld, ect all have their uses makes human the less desired pick.
The only class that seems to go human across the board is Rogues I assume for the stealth detection and heroic WFS. I guess with Cloak/sprint/shadowstep/every other thing that rogues have that is retarded they don't need Escape Artist.
XI Wiki

