This is just a short post to go over something that’s been talking about in the site’s comments (which people might have missed). Assassination rogues benefit hugely from mastery since they only need +171.45 mastery to increase their poison damage by 1%. With around 50% of your damage coming from deadly poison, venomous wounds procs and envenoms you can see why this is such a big deal.
However, if you look at the formulas for calculating poison damage you’ll find that the value of agility and mastery changes depending on your overall stats. Once you’re fully geared and your mastery is sitting around 75%, you will see a bigger increase in your poison damage by adding agility instead of mastery. I’ve calculated the cut-off point to be 69.5% mastery – as soon as your mastery gets this high you will see more poison damage coming from 1pt of agility than 1pt of mastery. Mastery is still better than crit/haste so you should definitely reforge, but it’s better to gem agility than mastery.
If anyone is bored and wants to see the calculations/formulas, have a look at the comments here.