The question when you have a low dps in your party is: why do they have low dps ?

Yeah sure if the tank forgot shield oath then the fix is easy (press a button).

But if a dps is not applying all his dot, why is it ? Laziness ? Not knowing he should ? What else is he forgetting ? Is he using hisoff CD abilities, his procs ? Does he know his rotation ?

All this take time. For people in my FC, sure, i will take the time to teach them and be patient. For people outside, i'm sorry, but it's not my job. If they can't put some time and thinking into how to best play their class, they can get into someone else's party and see if they are more welcome there.

And thinking that someone that is parsing 130 as blm on titan ex for example is going to suddenly jump to 180 because you tell them "hey buddies, don't forget to look out for those shiny procs, they will help you put out more damage ! " is completely insane.

In all cases this is no reason to be mean to them and to insult them. But, in a party labeled as "experienced", i would definitely not hesitate to say "i'm sorry, but your damage output is dramatically lower than what is expected for a dps in this fight. I would suggest you invest some time in looking for ways to improve it. In the meantime, i will have to replace you, as you are hindering this party".