Quote Originally Posted by Abriael View Post
They most definitely give players that make an extensive use of them a clear advantage over people that don't. So if they aren't a cheat they get very near to it.

The main negative point with addons is that their existance forces the developer to design encounters taking in account that they will be used, creating a further divide with people that don't use them. The problem has been mitigated by the ban on commercial addons, but it still remains as an underlying problem in encounter design.
No they do not, for example DMG metter gives no advantage, nor does threat meter, for the default UI already gives warning of when you are about to lose threat if you are a tank, or you are taking it if you are a DPS/Healer, all threat meter does is give an extra warning, it does not cast taunt or anything like that