As an update on this, we’re actively investigating a fix for legendary creatures that are not dropping legendary loot in some cases. We're testing this for inclusion in a hotfix that we’re currently looking to release later today, along with a couple of other issues that have sprung up following Patch 11 release.
We’re also looking into a separate issue that may cause non-legendary creatures to incorrectly display “Legendary” in their names with no star-ratings, and plan to address that as soon as possible.
We’ll keep you updated and will let you know as soon as we have a hotfix ready for release.