Currently my necro has only the node that enables cryomancers, however not frost lich.
When I (re)log the chance appears to be 50/50 to get a frost mage iso the plain one, however after a certain amount of time it’s either 100% plain or frost mages for the rest of the play time. (with only a relog to reset this)
So far this happened several times, unsure what the actual trigger(s) are.
*for me 100% is having cast that skill like 20-30 times in a row, including removing it from bar and putting it back to remove old mages, and still get the same mage, unsure what point the odds of having the same mage in a row is enough to be an actual bug.
Since I find this a bit odd bug, unsure what other info is useful.