Bonus armor for a prot warrior and other tanks gives an insane amount of attack power, and if you pick and choose gear carefully when building a 90-99 pvp set, you can do some RIDICULOUS damage. I recommend pairing up with a healer or ranged dps in order to counter some of the other gimmicky comps being played in the 90-99 bracket (like double brewmaster, mw/hunter, or… anyone with decent gear and some actual skill)
I wanted to give you a list of items for each slot that you could choose from to take advantage of this (as a Prot warrior or Blood DK mainly), and show you some games where I absolutely melt people with this gear.