Its all relative just like healing. How much TPS do you NEED? Enough so that DPS isn't threat capped, be it 800 sustained or 1200 sustained if you have some freaks in T6 gear. How much healing-per-second do you need? Enough to keep everyone topped off, mana regen, and a reserve for emergencies.
When tanking, I seldom gear for threat because I have "enough" I look at who is in the raid, the nature of the encounter and I consider swapping in an item or two. I can touch 1K but more often than not, I will go for more stam, more mitigation, more avoidance before going threat. Granted, I'm in T4ish gear, perhaps a little better. My tank is not currently my raiding main but I'm MTing ZA and Kara.
In T5 content, 1-1.2K DPS is pretty decent for most DPS classes. Factor in Salv and individual threat supression talents, etc.....How much TPS do you really need? And what are you willing to give up to get it?
your hat may be nice, but I have the little white tank top that says Legendary right across my boobs. I win. (or more correctly, H wins)