GS is totally rubbish, my wife's toon is only at early 4k GS and yet she puts out the same dps as my mage which is several 100 above her. When I am in Dalaran I see so many toons with over 5k GS and yet none of my current toons have hit 5k even though they are fully epiced with most of their slots filled with item levels 219 or above.
As someone said before, (might have been here) people are filling slots with high gear score items just to get the magical number required and then swapping those items out when the raid starts.
A good example is Sundial of the Exiled, really good trinket which has a lowish GS but is a really nice trinket with good crit and high proc on the spell boost.
A nerf I would like to see would be the annoying HoS timed fight, I know it is more for a MB than regular players but that fight is a pain