A brief blue post has cropped up on the US World of Warcraft forums that addresses the furor that has erupted since the launch of patch 7.3.5. After the update, players heading in to Warlords of Draenor and Pandaria raids noticed a 300% increase to boss health that prevented many of them from being soloed for the purpose of collecting transmog items and mounts. Blizzard has responded to the outcry that it was never "our intention...to greatly increase the difficulty".
According to the post, the team has been discussing player feedback since the release of 7.3.5 earlier this week and are prepping a hotfix that is expected to be released before the end of the week.
The issue with WoD and MoP raid boss health increase came as a result of the overall game tuning for players leveling new characters in older content.
We want to be clear: our intention was never to greatly increase the difficulty of soloing old raid content for transmog or mount runs, but a side effect of the creature health tuning we did for leveling players. We’re currently working on a fix that will significantly reduce the health of Warlords and Mists raid bosses. Thank you for all of your feedback and discussion on this issue. We’re sorry for the frustration, and we’re working to have you all back in there beating down those old raid bosses as soon as possible (hopefully before the weekend).
While the post indicates movement on the issue from Blizzard, it is interesting to note that player feedback on this issue posted to the PTR for 7.3.5 appeared well over a month ago.
You can check out player response to the blue post on the World of Warcraft forum.