Gearscore is useless. It just say what level of gear you got, nothing about what stats you went for, gemming or enchants and nothing about skills.
2 days ago i actually was in a group in HoR heroic where a warlock actually rolled against a healing druid for a mp5 with on use haste rating trinket "because he needed it to improve his gearscore"....
I lost count of how many 5.5k+ gearscore idiots that do shit dps, cant heal(tank isnt geared for this excuses) or cant hold aggro when tanking that grouped up with trough random finder.
I disabled the addon as its just sad to see how poor people can do compared to their gs. I only enable it at times to find out where my own gear is at, but usually i just check out be.imba.hu as it tells you where you could go with current gear.