I received an interesting email wondering about how parry works.
When you think about avoiding a Bosses attack your basic options are dodge and parry. Both Dodge and Parry allow you to complete avoid taking damage from that attack, so what's the difference.
Dodge is fairly straight forward, you dodge, take no damage and that's the end of the story.
Parry is similar. You parry and take no damage, but then your next attack gets sped up. Every weapon has what is called a Swing Timer. This is a measure how fast the weapon can be swung. With few exceptions, tanking weapons come in at 1.7 to 1.5 speed. That means that every 1.5 seconds or so (give or take a little raid buffed haste), you are swinging at the Boss. When you parry, that next attack comes even faster. So instead of swinging every 1.5 seconds, your next attack takes only 1 second. It's a nice benefit, but not without cost.
Parry and Dodge both work on a ratings to percentage system with diminishing returns. At level 80 it takes 45.25 parry or dodge rating to get 1% chance to parry or dodge respectively. Parry used to take more rating but the Developers changed that in Patch 3.2. Parry is still subject to more harsh treatment by diminishing returns. Basically as you get more parry, it takes more and more parry rating to actually get that additional 1% chance.
Parry versus Dodge decisions can come into play in many areas like whether to choose one piece of gear with dodge over other piece with parry.
So how do you decide? Lucky for us, Theck,Bringer of Numbers and Pounding Headaches, over at Maintankadin has crunched the numbers and given us a rule of thumb to go by.
Make yourself a macro and paste this text into it
/script DEFAULT_CHAT_FRAME:AddMessage("If ratio above 1.88 start getting Parry. Currently at: "..string.format("%.2f", (GetDodgeChance()-10)/(GetParryChance()-10)))
If your ratio is over 1.88 you need more parry, if it's not, keep stacking dodge.
Parry and Dodge are also considerations for gems and enchants. They just aren't considered very long, at least by me.
I can't see a situation where I could gem or enchant parry or dodge. Full disclosure, I do enchant parry on my gloves, but I'm getting Armsman more for the threat. The parry is simply a nice bonus. My gems are generally going to be Agility/Stam and Stamina. I might throw in a Def/Stam if I like the socket bonus. Just know that I only like socket bonuses that are 9 or more stamina.