In continuation to my earlier blog on evaluating your SimulationCraft results, this post covers the stat weightings (or scale factors) in much more detail. These are the numbers that anyone new to SimulationCraft will generally be looking for, they are the way you decide one piece of gear is better (for you) than another, the way you chose your gems, enchants, how to reforge and even which buff food and flasks you use. There are a few things to note about stat weights, firstly they are variable, as your gear evolves, so do they; secondly they are unique to you and your gear, this means that the websites proclaiming the definitive stat weights for your class are, at best, an approximation of an approximation – unless they've been calculated with your stats in mind they won't necessarily be applicable to you; finally, and probably most important, the weightings are a reference, and nothing more – unless you are absolutely perfect in your DPS rotations and positioning, your play style will have a far bigger impact on your DPS, use the stats as a framework for improving your overall performance, but don't expect getting your stats right to instantly make you hit 18k DPS.
A word on variability of stat weights
As I mentioned above, stats weights will vary with your gear (and the level of the mob you're fighting) I've knocked together this graph to try and illustrate this from the five examples I made for my last post. Notice how Mastery gains in importance as your gear (or buff level) improves. You'll also notice that Spirit and Hit are useless to me in heroics, that is because I've reached the hit cap (Spirit gives hit with the xxxxx talent). The other weights vary as your stats change, this is why it's important to run a simulation yourself, I'd even go so far as to run one each time your gear changes so that you understand what the implications are. If you're a more serious raider, you might want to play around comparing what your performance should be like with and without raid buffs so that you can adapt your unbuffed gear to give you the best performance when in a raid.