One of the supposed improvements with Warlords of Draenor was loot would drop and you wouldn’t have to run off and reforge it before using it. To get the numbers to reforge it you’d normally use an external application or website.
Now in Warlords of Draenor with gem sockets and warforged you still need to be using external applications or websites or have your spreadsheet handy for die hard theorycrafters. This is where mathematics come into play. While you’re best secondary stat might be X followed by Y that doesn’t mean in the overall mathematics of things that a gem socket and especially a gem socketed warforged wouldn’t trump what you “think” is your best item.
Let’s start with some basics ideas to introduce why the new loot system isn’t much better than what we had before:
Almost all simulations rank secondary stats from 0 to 1. The best is 1 and the worst is 0. Blizzard tries to keep the stats fairly close to 1, but it’s not surprising to see 0.5 to 1 ranges on some specs.
Let’s say your item has X stat of 250 with a value of 1 and Y stat of 100 with a value of 0.8. Overall it has a value of 330 (250 multiplied by 1 added to 100 multiplied by 0.8 equals 330).
Now here’s where the math comes into play. Adding up all secondary stats you want the highest total. Normally that works out you want the two top stats closest to 1, but adding a socket generally will make 2 weaker stats plus the 75 best stat from the epic gem overall better in many cases.
Let’s say now the item has a value of 175 of stat Y with a value of 0.8 and 175 of stat Z with a value of 0.7 but it has a gem socket. Just from those two stats you have 262.5. Add in a gem socket of 75 stats of X at 1 and you now have an item worth 337.5 that’s greater than your two best stats on your previous item. That’s not a huge gain, but still better than what you had before. Add in a warforged gem socket and it’s actually much better than what your “best in slot” list probably shows when comparing non-gem socketed, non-warforged items.
This doesn’t apply to odd situations like proving grounds, challenge modes, and timewalking because they have scaling/disabling of gems in them, but for current raiding the bottom line is DO THE MATH!