My warrior is now 90, i specced him arms because according to both noxxic and icy veins it's better below 500 Ilvl and what little i've done so far agrees with that.
is the Icy Veins stat priority of 7.5% hit-> 7.5% expertise -> STR -> crit -> haste -> mastery correct? and should I gem mainly crit or STR?
You will never gem haste or mastery.
If you want to take the gembonus (You´ll will find plenty information about which gembonuses are worth taking) you socket:
red - str/crit | yellow - crit | Blue - hit/crit | prismatic - crit. After that you reforge to 7,5 hit/exp.
If you don´t want to take the gembonus you´ll simply go for crit.
If you happen to not reach the 7,5 hit/exp cap, and ONLY THEN, you will have to go for red expertise sockets or yellow hit sockets.
Your stat priority is correct, with haste and mastery being ALMOST en par, with a slight advantage of haste.
What i've noticed is that you can go an MS-x-x-x-MS rotation as arms, where you use MS, then use 3 more skills, then MS again, with 2 of those skills being overpower. is this the right way to go? There's no arms guide on here, so i'm not that sure, but still, it seems pretty close.
Stolen from Noxxic (One of the many guides out there):
Mortal Strike on cooldown. Applies Deep Wounds.
Colossus Smash Use as often as possible. Watch for Sudden Death procs.
Heroic Leap if Colossus Smash buff is up. Not on the GCD!
Heroic Strike to dump Rage (70+) when Colossus Smash is up. Not on the GCD!
Execute on cooldown when target is below 20% health.
Overpower whenever available.
Slam to dump Rage (40+) when target is above 20% Health.