Finally I catch it. I think that proper description for this ability should sounds like
10% hits converting to crits when attacking the same target as an ally. AGAINST FLANKED ENEMIES
And it doesn't work with spells, for example if you prone enemies, then debuff them with cipher's Phantom Foes and then cast a lot of dancing bolts by your orlan-druid Minor threat DOESN'T WORK.
I made a few experiments with melee, ranged weapon and spells. I've beat an enemy by fighters, rangers, wizards and then attack the same guy by orlan. He crits a lot, but there wasn't any notes about minor threat in the log.
So the question is still actual.
How exactly hearth orlan bonus working?
10% hits converting to crits when attacking the same target as an ally.
For example, if my orlan-druid will cast some aoe spell like Dancing bolts after another wizard cast fireball, will it affect all mobs which was hitted by wizard's fireball? Or it works only with melee attacks?