I tried a few things on my DK for PvP.
I tried unholy, I can't play it for shit. Can't say I'm a great fan of the whole pet thing. Maybe if they let me sacrifice my ghoul I'd be interested.
At first I ran full PvP gear with 85 caps for hit/expertise. Kept on getting dodged and parried too much, so decided to go to the level 90 hit cap and reforge into expertise. That seems to be working for me.
Right now I run 433 helm with PvP Power gem and 450 belt with PvP Power, rest is Cataclysmic with full enchants for DPS and PvP Power gems.
For those of you following in the footsteps of the level 90's with PvP resilience stacking, you realise that all you're doing in a twink bracket is taking SLIGHTLY smaller amounts of burst damage, if they're already hitting you hard enough that you need the resilience you're most likely going to die in 4 or less hits anyway.
Quick example, I run up to you on my DK, my average obliterates will hit you for around 70k damage per crit on around 60% resilience you'd have with PvP gear and stacking PvP Power gems. This would be reduced to around 53.8k if stacking resilience gems in the same gear. Approximately a 30% decrease, sounds like a lot but when you have around 150 - 160k hp it really isn't.
PS. If you went full defensive though, so full stamina enchants and as much resilience as you could get, that might be worth it for arena. But for BG's where you're likely outnumbered anyway. It's all about dat PvP burst brah.