Even if you're not a hunter/warrior/warlock, you may find some of the information on it helpful. The resilience formula was actually changed in 5.3, and after a lot of trial and error I determined it to be the following:
Damage Reduction = 0.65 + 0.35*(Resilience/(Resilience+23133))
(The 23133 number is accurate to plus or minus 9 points.)
After patch 5.3, it seems like a lot of people (myself included) have been falsely assuming that resil is no longer worth gemming for, due to it being cut in half on gems without any other real gain. But for warriors, for example, it is actually easier to achieve 1% damage reduction through gems than it is to achieve 1% damage gain. It seems that hunters and warlocks still benefit more from gemming damage, but the point is that it is actually very close, close enough where personal preference should probably decide which you go for.
So to all the complaints of one shots and such, realize that resil is still a very viable option. If you are a blacksmith and were to go full resilience gems, completely ignoring all socket bonuses (not really recommended), then with a resil chest enchant and PvP meta you could reach 2895 resilience. This translates into 68.89% damage reduction, which means you would take 11.12% less damage than someone with base resil. Fairly significant, especially if more people start gemming like that, since that means damage would go down by about the same amount. If you are a blacksmith and gem for full resil without ignoring socket bonuses, you would have 2415 resil, which is 9.45% less damage than someone with base resil.
Please feel free to play around with changing resil values and such on the spreadsheet, to get an idea of how effective it may be for you. And while, unfortunately, I don't have enough time to try and generate stat weights for all of the different classes and specs, you can take a look at the three present and get a rough idea of how it might translate to your class. (Pay close attention to the "gem values" for both resil and your highest DPS stat, to determine which is more beneficial.)
Also, please feel free to review my math and logic and look for any errors. I think it's all sound and good, but I'm not a math major, and I love being proven wrong.