Already enough people too concerned about their damage that they won't block properly and/or stop DPS to move during fights. Damage meters would most certainly exponentially increase this problem.
Free Dragon pet maybe? ;D
This is a dead horse, in a duplicate topic, that has been covered, and discussed to death.
TERA doesn't have damage meters. We have no plans for meters. If your focus is getting to the top of a chart, you're DPSing wrong.