Blizzard always struggled to balance Hunters as their core design is very different from other classes- A mana using ranged physical damage dealing class, with secondary melee abilities (& a pet!).
This led to some very strange design choices like Tranq Shot in Vanilla. Giving some bosses a frenzy affect that only Hunters could dispell, with an ability that had no other use elsewhere in the game.
Due to this it’s often hard to work out what the actual intent was for various Hunter specs.
In original Wrath BM was used for levelling, early expansion PvP, & soloing old content. Surv for early expansion PvE & some PvP, & MM for late expansion PvE & PvP.
As others have mentioned the affect from ArP was nerfed several times during original Wrath. With the final patch balance having the lowest affect from ArP, MM, as a more physical damage based spec has been severely compromised compared to original Wrath.
Surv on the other hand has become more viable by being less reliant on ArP, plus by exploiting a couple of bugs that seem to have been unknown in original Wrath, allowing them to be carried in the expansion so far by the Trap Weaving playstyle.
Trap weaving is controversial amongst Hunter players as some really don’t enjoy it. The inability to trap on Twin Valkyr has highlighed exactly how reliant Hunter viability is on this unintended mechanic with all the Hunter specs being in the bottom 5 specs for every bracket on this fight.
In theory at this point in the expansion MM Hunters should be approching where they were in original Wrath as a decent DPS, but unlike other ArP dependent classes such as Fury Warriors they are still bottom tier for unknown reasons.
With Survival not scaling as well with gear as MM, chances of other weaveless fights, & MM underperforming, ICC is not looking very promising for Hunters.