I'm convinced SoJ doesn't exist. Since level 60 I haven't gotten a single one, all my fucking buddies have at least 2-3, some 5-6.
Hadn't seen one since shortly after launch, 2 months ago. 300 hours on my Wizard alone and just one SoJ. Then in the last 2 days, bam, 3 of them (fire, cold, arcane).
It's all random. Over a long enough time span, with enough drops, the probability of any particular item will eventually approach a guaranteed event.
With targeted gambling, the odds are significantly increased. So, save up shards and gamble rings, assuming you have no high priority 5 shard gambles.