Though not exactly answering the original question, this post was brought about by a question posed by Brigwyn from The Hunting Lodge on Twitter.
I don't really know when this started to be the "in thing," to check Gearscore before inviting people to a group. I don't know who started it or why. I just want to say, in my humble opinion (that you obviously wish to read as you're on my blog), that this is the stupidest thing I've ever seen.
There are multiple sites and addons that check the Gearscore of yourself and other people, and none of them do it the same way. So where on one you have a Gearscore of 5k on another you'll have a score of 2k. When someone asks you for your Gearscore, saying one could get you blocked while another could get you invited with stupidly high expectations of what your gear will turn out to be.
As far as I can tell, the Gearscore math works off of arbitrary numbers assigned to gear ilevel, gem rarity and enchant level. From what I've seen, there's nothing there about actual itemization, talent choice, experience...
What a useless, arbitrary mechanism.
I was in a ToC 25 where someone freaked out and left the raid because our raid leader didn't have a "good Gearscore." Though according to wow-heroes he did, apparently this guy's addon said otherwise. So he left, and we one-shot everything in ToC 25 with our PUG and our bad, bad Gearscores.
What in the world is the point of this Gearscore shenanigans? None of it matches up, you can trick it by just throwing on your vehicle-driving gear set. In fact, the only fights which Gearscore could be applicable would be Flame Leviathan, and even then...it's such a push-over without towers that there's really not even a need there.
I understand what it's trying to do. It's trying to streamline the process of accepting people into PUG groups so you don't have to go to the armory and check out their gear and specs and achievements yourself. But, really, there is no substitute to making sure, yourself, that the person who you are inviting is someone relatively competent in gearing, spec'ing and itemizing.
So, hey, stop being lazy and relying on a broken, arbitrary scoring system to make your decisions for you. And stop asking me about my "GS." I don't know it and I'm not looking it up.
To end on a positive note, if you still want to be super lazy, check out the Elitist Group addon. It's a little more in-depth than Gearscore tripe, but it's still no substitute for actually knowing what to look for in a PUG member.