fury is the way to go when you have top-of-the-line weapons and near bis gear. you being offspec dps you probably dont have the gear to support fury, so you made the right choice going arms. however....
you are still way under expertise cap with 2/2 wep mastery, you need 18 expertise (26 without wep mastery). this is hampering your dps alot since arms is a gcd-locked rotation, and a miss or dodge will kill your rage and kill your dps. grinding heroics for emblems needed for t7.5 legs will be a nice upgrade.
you should also try getting as many conquests as you can get to buy the 2 t8.5 tokens, conquest neck and gloves, and then some valor items like the t7.5 tokens and possible boots. get the crafted ulduar dps belt if you have the gold, along with a nobles card (works good for a block trinket too).
until then, dont gem arp since you dont have the gear to support gemming for it. wait until you have 30% arp from just gear, not gems or stance. so replace all your arp gems with str.