A group of friends and I are planning to grind to level 80 exclusively in instances. We are very much influenced by Xav's speed run video, and have done a few dry runs in Heroic Shattered Halls (which we assume would be comparable in difficulty to a 72 instance) and have been able to consistently clear it in less than 15 minutes.

My question is which set of gear to use. Should I stack block value (1054 in current gear) for SS and Damage Shield at the expense of attack power and hit, or should I wear my threat set gemed for attack power and hit (atk power increases TClap and SW dmg). Furthermore what defensive stats should I mantain going into WotLK instances? Should I keep 490 defense or sacrifice it for more aggro/dmg stats? What % avoidance should I mantain? I am in full T6/SW gear atm, and the healer and dps I am grinding with are in comparable gear. I know Xav runs it in mostly dps gear to make the run as fast as possible, but I would at least like to keep my 4 pc T6 bonus and sheild block value. I have acess to a ton of gear (accumlated while progressing from Kara) and any tips would be much appreciated.

I also intend to respec to a more offensive oriented prot build beforehand, droping Deflection and Anticipation to give me some more talent points to play around with.