Parry is a horrible stat to gear for, nonetheless gem for(!), so take those out. What I would do is switch one of those parry/stam gems to an exp/stam so you're capped on that level and the rest, gem for stamina. Unless it has +9 stamina socket, then it might be worth to gem dodge/stam to get that one as well. But for example the helm socket of +8 defense is not really that great to you. Note that excess defense isn't necessarily a bad thing, because it's still avoidance, but it isn't as vital as before.
When we're on the subject of improving your character, it might be worth to replace your weapon enchant with something else as well as your shield. Stamina on shield and maybe Mongoose on the weapon? You could also replace the shoulder enchant with stamina as well seeing as you have so much defense, if you got 10k honor lying around.
Given the distribution of avoidance stats on gear, you should never have to gem parry even if you are going for more avoidance (for whatever reason) as you'll pretty much always have less than 1.8x more dodge rating than parry rating (the ideal ratio for DR). Personally, I always go with expertise for red sockets when i can use the bonus, because it's both a good threat stat and great for reducing the chance you'll take spikes from parry hasted boss swings
Red sockets if you actually want the bonus, would be expertise normally for a tank, not parry rating. Most of your raw avoidance should come from the gear stats alone, and you gem to increase effective health or threat generation.
Health has no deminishing return, gemming for stamina is always acceptable if the socket bonus isn't really worth it and you already have your meta requirement met.
You should always do everything you can as a tank to ensure the success of the raid. Tanks are almost always the primary point of failure and of the three raiding rolls, and minimaxing for tanks is consequently very important.
26 agility on your weapon, multiple blue quality gems (one in your i-lvl 245 chest no less!) You sir, are a very naughty tank. Please fix and make your healers happy.