Problem is, sometimes people set that "1" on one person and then never change it for the rest of the fight, even when every fiber of your being is saying "Okay, we've killed this person a number of times now. This isn't doing much for us now." Or it's just on a target that makes no real sense. You trust the mark, to be a good sport and all, but then it ends up costing you dearly because it was not a good target.

Then there's the many times I've focused the 1, only to have my melee dps focus something entirely different. Sometimes I just give up and switch to the melee dps target because splitting damage gets us nowhere, even if I'm on the "right" target.