This is wrong on so many levels. If you're gonna join a farm party, at least let the leader know you haven't cleared it but will boot yourself out if you make party wiping mistakes.
People didn't do it because it's a DPS check. People do it because the fight is easy enough to solo heal so they just want to get it done faster.
I don't hate echo. It helps me make up for other people that are not as familiar to the fight as I do. You don't really need 20% echo per se. It just helps people recover from mistakes. It also helps killing the heart before circle bomb that so many people aren't good at dodging.