Relief pitching stats are not perfect, and ERA has long been considered to be an imperfect measurement of performance.
ERA is imperfect. This is not news to anyone who has been around baseball for a while. Is it fair when a starting pitcher leaves a runner on 1st base and a reliever comes in and blows up the game by allowing the next 3 batters to reach, including a home run? That runner on 1st base gets attached to the starter. Kind of a rip-off if you ask me.
What about all those low ERA numbers for relievers who you think are horrible?