Arms isn't getting any love. It's like a really good looking girl having an average looking sister. The more attractive one then gets the crap beat out of her, and now looks horrible (stand against domestic abuse!). The average sister now looks better than her formerly attractive sister, but still looks the same. Either way, when given a choice you should choose whoever you like the best.

The only spec that is burning up the charts, literally and figuratively, is fire Mage. But Arms are in excellent shape, ranging from solidly competitive on normal modes to outstanding on heroic.

For that matter, Fury is fine. It is currently within about 5% of the median, well within the margin where player skill makes up the difference for the vast majority of players. And the better your gear is, the better fury gets, more so than almost any other spec.

Good fury warriors still do excellent dps, but Arms really is strong this patch cycle.

I think that it's the fight mechanics that that are pushing Arms ahead, more so than the nerfs Fury took (though that DOES have an impact as well). On top of that the 4/5 T13 set bonus almost guarantees that Arms will have the CS debuff up for the majority of any boss fight.

The fist fight allows you to use the Jugger Talent frequently, causing MS to crit more often.
The Slime Fight supports Arms' Crazy AE DPS style (B&T, SS, and BS = 40K DPS easy).
The Pong Fight gives you free Rage for bouncing the ball back and forth, allowing the use of HS more.
The Frost/Thunder Boss allows Arms superior Mobility to shine.
The twilight dragon fight is all about sitting there and doing your rotation with the occasional interruption due to needing to hit the boss button.
I haven't done the other fights (I got sucked into SW:TOR, so I'm taking a break from WoW) outside of the LFR tool, so I can't really say one way or another on those.

It's not fight mech. arms has been theory crafted as higher single target and multi target fights, regardless of movement amount.