Okay, so we picked up this Blood DK for a 3v3 team in season 7... we've been practicing a lot and he hits like a truck launched from space. He stacks ArP and just absolutely destroys high-armor targets... so it got me thinking:

"What if I stacked ArP as well (instead of Agi)?"

So I got to thinking about my sets... do I even HAVE any ArP gear that I can run with in PvP?

Okay, so I need to keep the 4-set bonus for Feral (or do I?... yeah I think I do...), so let's see, I have the T8 helm, that has ArP on it. Sweet, I've got a ring with ArP on it. Sweet, I'm wearing bracers and feet with ArP on them...

All tolled, without looking for more gear or gemming for it, I have 201 ArP. After looking through WoWHead for ArP-grades (lawl), I find that I can farm the non-heroic ToC 5-man for a belt upgrade (I'm lazy and still have a Hateful belt >_<) with 47 ArP on it, and there are 2 easy ring upgrades with ~40 ArP each on them AND a socket a piece (which is better than my current ring).

That would put me up to ~290 ArP without gems... uh ohz...

Okay, I can get the epic ArP gems for 10k honor and a guild-mate cutting them... and I have all these arena points laying about with really nothing to use them on...

If I get these two rings, I will have 14 sockets and 1 meta... one of those gem slots has to be a green (to cover the blue/yellow reqs of the meta), leaving 13 gems for ArP... at 20 ArP rating a piece. Well blimey, that's 260 more ArP rating, which would bring me above the 550 ArP mark...

Holy hell... that's basically 45% armor ignore... before FFF which would bring it to 50% Armor Ignore.

... YEAH ... I think we're gunna go down this road...

EDIT:

DOH... there's Diminishing Returns on Armor Penetration above 7616 armor >_<
It's still extremely strong, but just not AS extremely strong.