People just need to realize that every party member is expected to do whatever is within their power to help the run succeed. This means tanks and healers contributing to damage, this means players performing mechanics to avoid unnecessary vuln stacks, this means using tools DPS have such as Feint, Addle, or Mantra to help reduce damage taken or recover it faster. A healer is simply the party member that can most effectively recover HP, a tank is the party member that takes the least damage from attacks, a DPS is the party member that deals the most damage. A role is what you excel at, not the sole thing you do with absolutely nothing else done whatsoever.