Well, according to RAWR 40% arp is already enough to make ARP better than AP and Haste.
It is possible to get over the crit cap with a arp based gear. With the right gear combination its possible to have the spell hit and expertice cap, 74% crit (with 3% of it over the cap) and 62% arp.
Nevertheless its hard to say if it wouldnt be more beneficial to stack additional crit over arp to supress the glancing blow chance even more.
What really surprise me though is that RAWR tells me that the common retail BiS gear from elitistjerks does only 12384 dps while the ARP based gear that I created does 12417 dps .
In case u want to test it urself with RAWR.
Thats the arp based gear: http://pastebin.com/fyXj7PDh
BiS gear from elitistjerks: http://pastebin.com/kWJPDEab

