ADWTCA on the lightforge podcast had an interesting point about new arena.
Right now Spikeridge Steed is still in 62% of paladin decks, but that's the player's fault, not the system. The system probably has Spikeridge Steed lower than a few other cards like in the lightforge tier list, but players will still always pick it, whether or not it's at the top or bottom of the 3 cards offered. Basically, the system is probably being smarter than the players.
Moonglade Portal, Blizzard, Firelands Portal, Shadow Word Pain, Shadowblade, Jade Claws, Defile, and Execute are similarly popular, and thus overrated compared to what Blizzard thinks.
With something like Defile I bet the system sees it as worse than it really is thanks to players misplaying it.
For all we know the system ignores draft results from decks that don't make it to at least a certain amount of wins.