Unfortunately, I believe elemental orb spells as well as flame arrows and other spells that are more than one attack in a single spell only allow sneak attack damage on the first attack. So the first spell of 10 orbs would have 6d6 sneak attack, as would the second, for 12.
It's like shuriken. You only get sneak attack, point blank shot, weapon specialization, etc. to damage on one of the three. Though I always liked the shotgun feel of a rogue with two fistfulls of darts (or acid orbs, or charged playing cards) doing 6d6 sneak attack with every one. But Skip thought that was a little unbalanced.
Ah, but the reasoning behind shuriken is that you make one attack roll for all 3 shuriken. The lesser energy orb requires one attack roll for every orb. Also, I don't get Dragon, so I don't read Skip's advice. Until there is official errata for the Tome and Blood, I'm going by my sneak attack arcane trixter god =) Besides, if a rogue with full attack can get 4+ attacks easily, my arcane boy should be able to get his orbs off =)
But, if indeed it is as you say, lemme work up a new one. The arcane trixter is increadably easy to abuse.