Quote Originally Posted by Xystic View Post
Having a warning system reduces 1 less challenge you have to deal with. When you have to pay less attention to certain mechanics because you have an addon or mod to do it for you, you now have fewer things to focus on, making encounters MUCH MUCH easier.

Anything that makes an encounter easier contradicts the argument that content isn't hard enough, including, warning systems.
Well. One way or another, endgamers are using it. But addons would let us do so much more. How about a friends list that lets us keep notes and provides a "last seen" date? Or an inventory management helper that lets crafters know what materials they have stored on retainers? A more detailed weather tracker for fishers? etc etc

Updated my OP to reflect this... this isn't an argument for DBM-alikes in particular, but I suspect those are one of the most popular third-party tools right now. Anyway, included more examples.