Your information caption for Fenryr is incorrect. The mythic two bosses have to be soloed completely in order to tame him now. Here is a blizzard link for that info.http://www.wowhead.com/news=262456/blizzard-posts-april-13-hotfixes-fenryr-hotfix-7-2-5-brewmaster-and-enhancement-
**this is your info: It was intended for this NPC to only be tameable after *soloing* the dungeon up to this boss, but currently works in a group. Just wait ~30 minutes after defeat for a "soft reset", and the tameable Fenryr will appear.
This needs to be updated.