it is random. Gambling is random. 9/10/11/12 do seem to come up more often in my experiences. Mining is random. If you mine in a crowd of non-afkers your chances of getting a gem are a lot higher than if you afkmine alone. Socketing is random. There does however, seem to be certain times for each server that increases the chances of socket...my wife made 2 soc boots and necky (from no soc), made a 2nd soc in her boots, and made at least 4 other socs in a 3 week time frame by spamming at a certain time to a certain time every night.
but than again, some of you will still think whatever you want and insist that its not random, that the gm's actually worked to create a non-random algorithm to help the players get items that luckier people make and sell for a bulk pack.