I can guarantee Square doesn't view this as a "problem". Anyone who joins party, PUG or Sub or Static, and clears a fight, deserves a fair shake at the rewards that drops. Even if they were carried or died a lot, they contributed the fight in someway that lead to the clear and deserve the chance at the loot.
Anecdotally, my 7/8 static has had to pick up a random healer every week since week 1 and every single week so far, the random healer has walked away with at least 1 item. As a team, this is a loss as that gear no longer contributes to our team's DPS the following week, but it helps that random person and w/e party they join next week. Even though we WANT to vilify these "PUG thieves", we all know we wouldnt have cleared w/o them and they deserve a fair shot at the loot like all of us.