your not expertise capped, thats alot of dmg that is going to waste, even if it procs overpower. arms is gcd locked and being at or very near the expertise cap will boost your numbers alot. why do you gem for crit? at 30% arp from gear, arp is your best stat to gem for (at least get to soft cap with arp gems). your weapon is also holding you back alot. try getting the 2h axe from h toc 5 man, and getting the t9 gloves to help on the hit that you will lose. nobles deck is best in slot trinket until twins in totc 25, so it is a great investment to replace your mirror with.