A suggestion: When you finish a fp, or small heroic or op, you rate the other players based on how well you feel they performed in their specific roles. So many votes would get you to tier I then II and on up. That way, when you use the group finder people can see exactly how "experienced" you are in that role. The vote would be entirely anonymous, and something like 1-10 with 1 being worst, 10 being best.
It will be abused by guilds that will create guildrules to max vote for guildmembers you team up with.
Sadly this will not serve any purpose in the end, it is a good suggestion though