Honestly, when someone you don't know kicks you and states "so and so did this much dps" I wouldn't be too worried about it. Most of the time they are just making stuff up or referencing something they heard with no proof to back it up. There are also people who are just amazing at this game, but you don't need to be as good as them to do stuff like bismarck ex. So yeah, don't beat yourself up over that.

With that said, I've cleared the fight with two of the four dps having lower numbers than you did. So if you can stay close to 600 you aren't significantly weighing your team down to a point where you need to be kicked--especially if you are handling and doing mechanics correctly.