Oh, don't get me wrong, I'm not saying it's -bad- to have PvP pieces, I'm just suggesting to round out your defense +/- a couple points instead of filling it with resilience.
Sure, be.imba.hu cries at me for being over the cap, but I'm sitting at 415 defense, and some 100 resilience. The resilience ONLY exists because, well, the S2 shoulders are some of the best shoulders out there for tanking.
And the S3 gloves ARE arguably the best Feral gloves in the game. Why? The equip bonus.
It adds an interrupt to maim.
With the new instant shifting / shifting between forms, you can make a tanking macro using these gloves. It's a tiny bit risky, and if you're low on HP or Armor I would NOT suggest it (or if you have high latency).
I don't know the exact terms, btw, this is just the general idea.
/cast CatForm
/cast rake
/cast maim
/cast DireBearForm
What this does is an almost instant interrupt.
It assumes much, the biggest assumption being that you have the talent that adds energy / rage as you shift. The second assumption is that your healer can keep up with the added damage in kitty form. An alternative is to add /cast Barkskin to the beginning of the macro to help with mitigation.
If you have higher latency, it can take too long to be useful on short casts.
The reason Rake is present is because it's a cheap combo point, and you need one combo point to maim.
Other than the shoulders and gloves though, I don't -really- see many other pieces of Arena gear being terribly useful.
Maybe the Headpiece if you're like me and stuck using an AH green. I believe there's a nice leather tanking head from the Gorefiend questline in SMV, but it could be DPS. I haven't completed it yet due to severe laziness :)
The weapon is, IMO, not worth it for tanking. You're either going to spend a TON of time farming AV, or more than a month in arenas.
In that time, you SHOULD be able to scrap together enough SV runs to hit exalted and get your Earthwarden.
Also, you can get Defense Rating shoulder enchant from Aldor (I -believe- Scryers has one too), and an Defense Rating head piece enhancement from Keepers of Time to fill in small temp gaps.
Chances are, though, if you have the Clefthoof Set, the Necklace, and the Earthwarden, you're going to end up overcapping your Defense Rating. It's no biggy, but at that point you can add the Attack Power or Dodge Rating enchants to your head and shoulders, and remove any DR gems you've got in there and stick in Stamina or Agility / Crit / Dodge / Hit rating gems in.