It's not that simple. I did a pug last week where the raidleader invited his friend DK with a blue weapon and overall just bad gear. He didn't play that bad but if I have to roll against someone with gear that is not even good enough for the instance who does 7k dps and I am in full T10 doing 14k dps I don't really think that is fair. But pugs are pugs and I could have left. I didn't really care, but it's just an example.
So guilds or GDKP runs!