OK to begin with,
You are not hit capped against a raid boss change the boots enchant to icewalker and that should do it. Your third glyph should be bladestorm (instead of execute)
Your gear is just fine you are at softcap of ArP means when the NES trinket procs you should be 100% arp. You need to time your attacks with that proc to max out dps.
You have a wrong gearset for arms, Arms uses t10 hands and crafted legs as expertise is not really that important for arms as it is for fury. If you can afford try to aim for t10 4pc (chest shoulder helm hands) + Legplates of Painful Death. The wrong gearset is also the reason your expertise is crazy high.
Your opener is fine, so go Charge - Rend - MS - (now procs) Prioritize Overpower over execute. After that just follow a simple priority,
Rend > MS > OP > Execute > Slam
so basically what I am saying is just change your rotation slightly instead of refreshing MS debuff, you have to use MS at every cooldown. Also prioritize overpower over execute.