Yes, Yes and No. If you watch past normal and heroic raiding, then you are looking at a very small procent of the players who have play hunters. To take the point of Blizzard directly, they don't balance the game for high end mythic raiding and they have said that multiple times. Mythic will never be balance so don't expect it. Hunter works very well in heroic and normal raiding, yet you have the audasity to call it broken just because it is not top 5 dps on all fights in mythic. You seem to be crying about MM being the only "viable" spec in mythic, yet that is how it has been for many classes through time. As a rogue main, i can tell you how much our class have been about 1 spec at the time since MoP. You are not unique in the situation to have a dominant spec, so don't go all "Blizzard hates/ignores/treats us special bad" on me, because you are in the same situation as everybody else.
Alot of people in here seems to speak from a very high point of view, where they expect their class/spec to be atleast top 5/10 dps on every single boss, but Blizzard have already said, that they want classes/specs to have clear places pros and cons. With hunters it seems like the pro is on multi/aoe dps and the con is single target. So plz accept, that while you are bad on some fights, you also have the fights where you are godlike on. Everytime where you put up some numbers from Guarm or Ursoc, i will just counter it with numbers from Illgynoth, Helya or Dragons.
And also, i have nothing to say about 7.1.5 changes. Ion's comment was only about live and i will therefore only talk about live stats.
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Well then bring this up with Blizzard. Say that you want a tank or healing spec to go to, since your dps is "bad". Maybe they will make survival a tank
That should solve your problem