While it it does sway the damage out put on heavily armored targets such as paladins and shamans while up, it's not as much say against a Rogue, Mage, or Priest. It will be just ArP, good against classes with higher armor, but lower armored classes are better just go straight strength.
I do foresee it getting a nerf to maybe something around 60-75% Armor Reduction, and Sudden Death decreasing the chance to proc as often (Like say once every 12 Seconds can Sudden Death Proc or something).
Overall you do have to realize this is an ability that Blizzard has already stated they enjoyed and want in the game. Not to mention It's one of the few abilities without scaling other abilities to ridiculous rates that will keep Arms PVE viable.
Also just a question, Why is it ok for Ele Shamans, and other casters to have huge crits but its not ok for melee? Especially when they're using a single slow weapon?