Originally Posted by Whitefyst

The information for which you have asked will not necessarily provide you the right answers for your situation since the correct answer varies on gear, raid buffs/target debuffs available, player execution, RNG effects of both attacks and negative affects on you, etc. Furthermore, what is the correct answer for one character may not be the best for yours.

In general, for MM it is best to gem agi and agi/crit gems for maximum DPS until you get to some threshold, which values depends on the given situation, where ArP becomes more effective than agility. This is usually as you near the passive softcap if you have an ArP trinket or hard cap values since the benefit of ArP increases exponentially. This is because the benefit of ArP is the inverse of the benefit of armor, which has diminishing returns for each unit of armor added.

Some reasons that give more weight to agi gemming include:
- If your guild's strategy often has you attacking targets that do not have full melee debuffs where your physical attacks, especially your ArP is not as beneficial. This includes fights like Northrend Beasts and Jaraxxus where you may be asked as range to take out the Snobolds and Mistress of Pains/Infernals instead of staying on the boss with the melee the whole time.
- Fights with a lot of movement. The standard standstill MM rotation of CS->AiS->SSx4 or SSx3 depending on glyphs (with a variation with AiS before CS) has a high ratio of physical attacks to non-physical attacks at 5 or 4 to 1. Hence, the standstill fights provide a lot of weight to the benefits of ArP. If you are moving a lot, the benefit of ArP is decreased in that a smaller portion of your shots, especially if you sub in a ArS, and your damage are physical attacks.

Looking at your gear (with assuming you have the Greatness Card in the first trinket slot instead of the medallion of the horde), I would first suggest changing the agi/crit gem in you ranged weapon to a agi/hit to get over the hit cap for a 4.3 DPS gain. Then I would suggest moving the Nightmare's Tear from the yellow socket in your ring to the blue socket in your legs to pick up the 6 agi socket bonus for a net of 2 agi. Then I would suggest replacing all ArP gems in blue, red, and belt buckle sockets plus the yellow socket in your chest with agi gems and all other yellow sockets with agi/crit gems to pick up socket bonuses. Doing so provides a net gain of 85 DPS in the spreadsheet's ideal situation of no movement and all melee debuffs and a net gain of 92 DPS in the ideal fight situation but where lacking melee debuffs on your target. It would also provide a relative net benefit on movement fights as well.