In regards to rotations - two "possible" good things are coming:
They have a one button rotation for ultra casuals. Continues your rotation for you when you get distracted, basically, at a minor DPS loss. Everyone thought it would be terrible, but by all reports that Ive read on it have basically said that its been an overall improvement on the lower end for people. For example, I never could quite figure out the rotation for my Warlock and would constantly be a good 200-300k behind another Warlock with worse gear at the beginning of War Within. Supposedly, even if he has his rotation perfect - Ill only be behind him by 100-200k instead (if it was available in that situation).
If you watch the Q&A, they blocked off a lot of strings in the UI that deadly boss mods, Big wigs, etc. were using to trivialize content. I imagine that if raids and Mythic+ are designed with that in mind, that'll also bring up a lot of the people on the lower end, too.
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I'd like to think that a lot of the bullshit that raid and dungeon bosses do will be culled back to be more understandable at first glance, like FFXIV type shit. But every time Ion has mentioned cutting off Combat Addons at the knee's - he's quickly followed up with "Our own UI will now incorporate timers, bars, etc." ... Which, Im more accustomed to think the worst first, and that we'll just end up with a shitty version of DBM and wish we had our own player made shit back.
Guess we'll just have to wait and see.