Songs:
1. become visible crow 三足烏 - 流派未確定
2. Three-legged crow～三足鳥～（Battle　Version）- 流派未確定
Recorded via Fraps@60FPS

This boss is tough. Very tough. This requires relatively high DPS and unfortunately, some mechanic dodging via the Advanced Target Dummies/Cardboard Assassin.

Glyphs:
Glyph of Cloak of Shadows
Glyph of Evasion
Glyph of Recuperate

Covering the basics:

Much like the normal mode encounter Ta'yak will still stack Overwhelming Assault, spawn tornadoes, and use Unseen Strike.
In addition to these abilities Ta'yak now has a new ability called Blade Tempest.
When Ta'yak casts Blade Tempest all players will be pulled into his melee range causing them to take 34200-37800 Physical damage every 0.5 seconds for 6 seconds. Simply run out of his melee range to avoid the damage.

Mechanics and what we should know:

Overwhelming Assault - This mechanic is brutal and we must do what we can to try and reduce the stacks. The way I avoided this was by dropping a target dummy and then vanishing so that the dummy takes the 2nd stack allowing me to drop a stack during Blade Tempest. This requires very precise timing.

Unseen Strike - Yet another very dangerous mechanic in that if you don't mitigate the damage you will die very quickly. The best way to deal with this is by using the Cloak Glyph with Feint. Extra avoidance on gear can also help. Using Smoke Bomb is also a good choice on top of Feint+Cloak Glyph

Wind Step - This DoT is going to be active for the entirety of phase 1 and is very annoying. It will deal roughly 16.5k Physical damage every 2 seconds.

Phase 1

I feel thoroughness is required to accurately explain this phase.
Approximately 15 seconds after pulling Blade Lord Ta'yak he will apply his first stack of Overwhelming Assault and at 30 seconds he will use his first Unseen Strike be ready to Feint+Cloak. At 35 seconds he will resume auto-attacking and at approximately 40 seconds he will use his second Overwhelming Assault. This is where the Target dummy comes into play.

Since we know at 40~ seconds he will use Assault we need to be prepared, drop the target dummy (in his melee range) slightly before and be prepared to vanish between 39.0-39.9 seconds. Once vanished delay ambush for a very small window because we do not want to immediately pull aggro and take the stack. If you succeeded you won't gain a new stack and the prior stack will drop off. This doesn't mean you instantly win but it does give you ample time.

At approximately 1:32 seconds Blade Lord Tayak will cast his second Unseen Strike. Cloak of Shadows will just be coming off CD as well so be ready to Feint+Cloak+Smoke Bomb this. (Once the Debuff reaches 2 seconds you are stunned and cannot act) Since his next ability is guaranteed to be a Overwhelming Assault use your Health Potion after the Unseen Strike because it is going to be an incredibly close fight at this point. Make sure you do everything in your power to stay alive such as Shiving on CD.

Once phase 2 starts it's pretty much a free win. Recuperate will out heal the ticking damage (Feint-able).

Armory: http://us.battle.net/wow/en/character/garrosh/Koshi/advanced