In V1.1.7.0, we are going to make a correction to the Crucible and Shattered Realm loot tables that involves the removal of base game Unique roguelike MIs from their loot tables.
This was already the case for Unique MIs from the expansion roguelike dungeons and was inconsistent.
So I guess if your hope is to farm them from the Crucible or Shattered Realm, you may want to do so quick! Although honestly they were rare from those game modes to begin with.