Blood Parry?

[Sflame]

Why are Blood Tanks gemming and reforging pure Parry? They even reforge out of Mastery to get more Parry.

Examples
http://us.battle.net/wow/en/characte...otikz/advanced
http://eu.battle.net/wow/en/characte...k/Auk/advanced
http://eu.battle.net/wow/en/characte...nerno/advanced

[Cryopathy]

1) Parry gives you more DPS through Riposte, more RP generation through Scent of Blood, and more of both through more melee attacks from Parryhaste
2) In 10-man raiding especially, tank DPS is important* and there isn't enough incoming damage most of the time to warrant gearing for full Mastery

Combining the two points above, Parry is a good way to increase DPS while not hurting your survivability too much. You gain a lot of DPS, and your total damage intake is roughly similar, but your damage intake may be spikier and is less predictable.

*Just one example: my guild beat Heroic Spoils by about two seconds last week, we would not have killed it if I was geared for full Mastery.

[Deleted]

More importantly, why parry, and not dodge ?

If it's all about maintaining the Riposte buff up, then balancing dodge and parry would be the wisest thing to do. Except it's not.

Parry gives you the ability to reset your swing timer, which not only boosts your dps, but also gives you even more scent of blood procs. Which is always nice.

[Nillo]

Well the difference between balancing parry and dodge is already extremely low
The difference in uptime of riposte is even lower.

[potatoe]

You've already received some great answers.

There is a whole thread with some pretty good commentary about taking avoidance (specifically, parry).

Blood Tanking Wanting more DPS

My takeaways from the thread:

Parry/Dodge
Gives 75% of dodge+parry as crit.
http://www.wowhead.com/spell=145676/riposte

Parry Haste
Procs when you parry an enemy attack.
Bosses don't proc haste when they parry anymore, but players still do!
For this reason, stack Parry way over dodge. Do not try to even them out. source 1 / source 2.

Scent of Blood
Increases Death Strike healing by 20%. Stacks up to 100%.
Procs on dodges/parries (avoidance!) and autoattacks (parry haste!).
http://www.wowhead.com/spell=49509

Most people in the thread are advocating something like the following stat priority:

Hit+Exp to 7.5% > Mastery to 150% (or whatever makes your damage smooth/comfortable) > Parry > Dodge > Other