My FC actually had to blacklist a certain player because they kept coming into our farm parties and causing wipes MULTIPLE TIMES. This person was very clearly not capable of farming the fight in question, yet they joined every single farm party that went up for that fight. And the worst part of all? They NEVER improved, not even a little bit. They kept on making the exact same mistakes even after people pointed them out.

If you can't reliably one-shot a fight, then don't join a farm party for it. It's not that complicated.