It's silly to be a damage dealer and not actually know how much damage your doing is. When I switched from my healer to dps the first time I had no clue how to improve. I remember doing a trial or something and I thought my dps was okay but someone said my numbers and I was shocked how low they were. That made me improve and since then I ask people with a parser what damage I do. If I never knew my numbers I would be a burden to the team at higher level raids.