In response to the 10 Rage Slam rotation:
You can simply macro /cancelaura into Slam and spam away. That just leaves WW as an AoE/emergency dump ability.
For the rest:
Thanks to Headlong rush, you gain 30 Rage every 2.4 GCDs, with crit chance of getting double.
Excluding the 10 Rage Slam rotation, you will generally have enough empty GCDs that you can shift (parts of) them around to have 1-2 'used' GCDs after each white swing.
That means your gameplay boils down to this:
0. WAIT(!) for white swing to grant Rage
1. MS > talents, if CS is not nearly off CD > Rend > IV/WW (keep 30 Rage for MS/CS)
2. CS > above (spend it all)
Waiting that 1 GCD with CS allows you to get in 2 white swings, which means not only more damage, but also that extra 30 Rage at the end you can spend on another Whirlwind for the extra damage. At 25% Haste (+lag) you also gain a major breakpoint here, allowing you to just fit in another MS in a CS window. (with the multistrikes coming in around 30% Haste)
This shifts a lot of gameplay from ability mechanics to 'hidden' choices such as the Haste breakpoint, waiting for white swings and timing dead time around CDs and Rage income. This shift is opposite to the intended goals of making specs easier to understand. (especially without a swing timer addon)
The current style of Arms gameplay feels
a) very reactionary. (All ability uses are dependent on factors out of your control)
b) boring. You are always waiting for Rage income and outside of the small effort of MS CD control, it's simply CDs > ragedump.
I always considered Arms to be a cool headed Master of weaponry and controlling the flow of battle. Hence they were always aimed towards Battle Stance and not Berserker Stance, as Fury was before. This goes completely out the door with the current state, where you are, in essence, reacting to white swings.
I would much prefer as Rage for Arms was considered more of a resource emulating the flow of battle (think towards combo points) than "RAWR MAD". If I were to have to redesign Arms, here is how I would approach it:
(*) Unyielding Strikes does not need be the final name for this effect.
- Rather than increase the Rage from white swings, keep Slam as a baseline ability that does low to medium damage and generates 10 Rage. This will make it feel as if you're trying to knock open your opponent's defenses, preparing for a large blow.
- With this active Rage generation, keep Mortal Strike as it is. That means you can always generate the Rage for MS in between uses, regardless of white swings, and the Rage dump play will come from replacing Slam with an ability that uses up Rage. More importantly, you can actually DO something to pool Rage for burst windows.
- Between Rend, Whirlwind/Execute and Ignite Weapon there should be enough Rage dump choices in your rotation to create enough interesting gameplay without becoming too complicated. CD talents add to this as a they become abilities that effectively replace Slam in your rotation (thus 'cost' a bit of Rage/damage) rather than just extra ways to fill up dead time.
I could see Ignite Weapon replacing Rend though, keeping it on GCD and shifting the (boosted) over-time damage from target to player.
- The current Slam talent could be replaced by several other options. Between the passive Rage from Rend and the free damage Execute procs, you could increase active Rage generation and add to rotation complexity with something like "Rather than always generating 10 Rage, Slam now gives a buff for 2s that allows the next Slam to generate 20 Rage." Or something like "Slam critical strikes have X% chance to grant Unyielding Strikes(*), reducing the Rage cost of your next Mortal Strike by Y". Heck, you could even put in Heroic Strike here!
To me, this seems a far more interesting way to play, without necessarily introducing deadtime & white swing gaming.
It would also solve the issues with Haste as Tengenstein has mentioned.