submit to the in game bug report for the lucid minor failing to apply stacks these forums are getting us no where. Sooner or later they will have to look at it
Pretty sure its because Mythic raiders don’t play frost but ehhh I just got focusing Iris rank 2 last night from a ML 9, so more and more getting closer to switching to fire which Is probably what they want 
Prolly, I do know from a very reliable source that the more in game bug reports CS gets the faster it will get fixed. It is about all I can say on that however so please spam the in game bug report daily.
Blizzard I feel as if they are losing there way a bit. This entire expac is about the neck and the legendary cloak yet something is beyond broken within the game directly related to the neck and it goes on ignored forever... But then again since 6.0 frost was hardly touched or tuned until just recently. We was generally nerfed.
We didn't even get BFA love but based on the quality of what I see we got exactly that... BFA love. Sorry ranting... I just cant fathom why they would permit such a bug to exist for so long especially since it was reported to them back in the PTR OF LAST YEAR and they have video and SS proof from a multitude of people ranging from in-house to players.