1. Glyph of Bloodletting
This change was made, I believe, with the intention to reduce our DPS penalty when forced to use Mangle. Unfortunately from our simulations it will not do anything.
Here are the simulation results (based on 410 BIS gear vs Ultraxion) with various Glyph options.
Glyph of Rip + Glyph of Berserk + Glyph of Mangle = 47788.37276 DPS +/- 5.78864
Glyph of Rip + Glyph of Berserk + Glyph of Bloodletting = 47353.60084 DPS +/- 5.47222
Glyph of Rip + Glyph of Bloodletting + Glyph of Mangle = 47638.99752 DPS +/- 5.56853
Glyph of Bloodletting + Glyph of Berserk + Glyph of Mangle = 46976.64711 DPS +/- 5.56459
Which means using the new Glyph of Bloodletting is actually a DPS loss compared to our 4.2 best glyph setup, and doesn't do anything to relieve us of the penalty we face
According to feedback from the PTR, Ultraxion has to be meleed from the front, but he has a mechanic that doesn't allow him to parry. If we compare our DPS against a normal boss that can be shredded from the rear and a boss like Ragnaros (in 10 man) which is meleed from the front and can parry, here are the simulation results:
Normal Shreddable Boss: 50683.32362 DPS +/- 6.4216
Ultraxion: 47788.37276 DPS +/- 5.78864
Ragnaros: 46202.91148 DPS +/- 5.96674
This means we are looking at a 5.7% DPS penalty against Ultraxion where other Melee DPS will be facing 0% penalty.
This is actually more severe than the 8.8% DPS penalty against Ragnaros (who can parry) because other Melee DPS will be facing some penalty (not sure exactly how much) from parry.
Dragon Soul has a lot of Expertise Rating in leather agility gear - possibly way too much. Our optimal collection of BIS gear has 1369 Expertise Rating, reforgeable down to 824, which is still over the 781 softcap. More details @ http://eu.battle.net/wow/en/forum/topic/3010801378
I hope this helps in your 4.3 Development. If you need more data or clarification, please feel free to contact me directly. Thanks!
EDIT: Added section on Expertise