is armor good for a tank dk?

i was thinking about getting the valor trinket, which gives armor. the trinket gives 1285 armor, which only reduces the physical dmg i take by about 6 or 7 percent, is it worth it?
If 1285 armor gives you 6-7% dmg reduc I have to wonder if you're wearing cloth. In my tank set 1k~ armor gives me .5% dmg reduction.

Flatline damage reduction is potent and beats out rng factors [dodge/parry] simply because you can always count on it happening. Thing is though, imo, a mastery trink would offer more then armor. It would also depend on where your armor currently sits. if 1200 armor would offer that much dmg reduction then it will stomp any other stat I believe.
Pretty much what Cal said.
I would rather a baseline flat damage reduction than a CHANCE to take no damage at all.

In my opinion having tanked to 85 and then switching to PvP, Blood Dk's should go as followed;

Hit Cap; Expertise Cap; Mastery; Armor; Stamina; Dodge; Parry

Dodge before Parry because you're naturally given a lot of strength which contributes to parry, So you should have more Parry than dodge, however do to diminishing returns you want these numbers as close to each other as possible.