I would honestly replace all those parry gems with 8 dodge gems asap before anyone else inspects you Parry Gems are a big no no in the warrior community. Its worth spending the gold do it.
an 8 dodge gem will offer a bit more avoidance then an 8 parry gem. The threat gain from parry is very very minimal and not worth the loss in avoidance.
On bosses that you are coming close to dieing on use the commendation of kaelthas It may be the best tanking trinket in the game. The 57 stam on it will make up for some the HP loss you suffer because you gem for avoidance.
You don't really need to listen to me though this blog will answer your question for you.
Avoidance outside the Math: Dodge, Parry, Defense... Block? - Warriors - TankingTips.com