Its really up to what you want to stack on the piece. Lets take the 8dodge for example, you have a choice between a 30stam gem and lets say a 10dodge/15stam gem (to meet the bonus). So you would be losing 15stam but gaining 18dodge.
Itemization wise that works out well but is it an avoidance piece? I basically do that calculation with all my socket bonuses. I usually find though 4dodge, 6stam, 4defence aren’t worth chasing but its always worth testing.
As a Warrior, I'd rather start stacking stamina. I assume you're not equipped with the highest tiers of loot seeing as you're going for defense bonuses. Stamina stacking would make you a more viable tank for later raids (especially in the eyes of non-tanking oriented raid leaders who see little beyond your HP count).
i stack pure +30 stam gems, except for the +10 dodge and +15 stam gem required for the meta to work.
I never notice myself being down on avoidance. The only socket bonus I would take would be a +9 stam or + 6 stam if it had blue sockets or 1 blue and 1 red and I could replace my dodge+stam gem from another piece of gear.
Well... All socket bonuses are worth looking at from a pure standing power perspective, I think. Except for stuff like expertise(when you have enough), and parry/block rating(One is worth little on most gear setups and the other 'caps'), any socket bonus that doesn't drop a critical stat is a good bonus.
I generally go for 30 stam gems. I have a 10def 15stam in my helmet with a 12stam socket bonus, a 10expertise 15stam for my meta in my crafted belt with 9stam bonus, and a 10hit 15stam in my boots, with a 9stam bonus. I feel that sometimes threat stats are worth more than a few stam.