I've made it no secret that I was really upset with the changes to Arms in Warlords of Draenor, taking my favorite Warrior spec and gutting it of all that made it interesting. Well, the good news is that they're rebuilding it in such a way that it's regaining some of the things I liked about it! It's not exactly in the place it was in Mists of Pandaria, but that doesn't necessarily mean it's worse. It's almost certainly better than it is in Warlords live right now.
As usual, the big caveats here are that this is in Alpha, and many things can change from now until Legion goes live. But we can probably expect these bare bones to work mostly the same as listed here.
So let's get into it!
Mortal Strike is still the big centerpiece of the spec, and they're sticking with the Warlords idea that this is your hardest-hitting attack that you'll want to use on cooldown, costing a modest 20 Rage, with a 6-second cooldown.
Slam you'll actually get at level 1 (players will now start off with a spec before they get to switch at level 10, and I assume Arms will be the default for Warriors.) It gosts 15 Rage and has no cooldown, but does not do as much damage as Mortal Strike, so presumably you'll use this to burn off excess Rage while MS is on cooldown.
Execute is its old self, costing 10 Rage but consuming up to 30 additional Rage to deal big damage to targets under 20% health, becoming your main Rage-spender in Execute range.
Colossus Smash is similar, but rather than letting you ignore the opponent's armor, it just increases the damage they take from you by 20% for 6 seconds, which I think works out to more or less the same in PvE. It has a baseline 45 second cooldown.
Most importantly, however, Tactician is a passive that causes your Slam, Whirlwind, and Execute to have a 20% chance to reset the cooldown on Colossus Smash, which you might remember as being more or less how the old Sudden Death worked (actually, technically speaking it was the middle-aged Sudden Death. Old old Sudden Death, from Wrath, actually worked how it does now, affecting Execute.)
Whirlwind is more or less its same old self, costing 30 Rage.
However, Cleave returns as a real ability, doing damage to all targets in front of you and increasing the damage of your next Whirlwind by 20% for each target it hits up to 5.
Recklessness is now a 1-minute cooldown lasting 5 seconds that gives you a 100% crit chance.
Mastery: Colossal Might increases the damage and damage bonus of your Colossus Smash, with 20% for both baseline.
Also, interesting to note is Defensive Stance, which reduces damage both taken and dealt by 25% until cancelled. Since all tanks will now always be in "tank mode," without the need of stances, this freed this ability up.
So the rotation is, I think, not too hard to figure out:
1. Colossus Smash on cooldown, particularly if you get the Tactician Proc.
2. Mortal Strike on cooldown.
3. Slam if you will still have enough Rage to do a Mortal Strike when it comes off cooldown.
In AoE, you might just toss everything out and alternate Cleave and Whirlwind (though given that Colossus Smash is free, you might as well toss that back in.)
Notably, both Heroic Strike and Overpower return as talents if you want to add some wrinkles and push Slam down in the priority list.