There are certain things the have always annoyed me, like when someone refers to a female character as "him". But in this case, I can't agree with you guys.

In group play, people use the job abbreviations for tactical instruction, not social purposes. The strategy that they are trying to employ is likely a broad concept that isn't specific to a certain person or even the job. And considering how every boss in this game has a strategy to it, people tend to explain these things often. Typing out the broad concept makes more sense, rather than trying to address everyone by name.

In Military, they will address people by rank. Your commanding officer isn't going to walk around calling every soldier by their name.