Sort of like the fire/ice mechanics in some trial encounters, but instead the player has to keep moving while attacking to avoid it. I think it would be a good thing to add in, as I've found that the primary cause of enrages in savage PUGS I've participated in was due to DPS or tanks stopping their damage anytime they moved, even when in proximity to the boss. This can be a control scheme thing or just a result of normal encounters not requiring a run-and-gun approach to succeed. A "speed bump" mechanic to get the players to start thinking about how they can do that before hitting end game would be better than finding out in an 8-man savage/extreme group.

Savage encounters are one of the worst places to learn about this because the person in question doesn't know he's supposed to be attacking when moving and everyone is way too focused on mechanics to notice him. So by the time someone informs him he needs to attack while moving, it usually took four to six attempts to notice it.

So again, a mechanic that requires movement and actions at the same time to avoid damage, kind of like the "ice" mechanic on some trials, would probably be a good addition to the game's end-game dungeon encounters, if only to get players thinking about how to do that.