Imagine this
(Numbers don't accurate, they're here for the sake of making my point) :
You're in a static on Midas Savage with an average DPS of 1000. You know the content by heart, you farm it every week with ease.
One week, your static can't play, so you join a Party Finder to get your loot. But in this party, there are seven uberstuffed uberskilled players who do constantly 1200 DPS.
After two wins, the leader says that you can't stay with them because your DPS is too low and the runs take too long.
Will you go "Ok, it's fair, I'm bad", or "Dude, WTH ?! We won two times, and I farm it every week" ?