This will essentially have the same effect as skittish weeks, it's mostly there to fuck with melee dps but instead of every couple of weeks it is now used as their crutch to balance m+ all the time. It will certainly effect tank populations at the lower end of the scale, even more so some time into the expansion, because who would queue into a heroic when you can be sure to encounter a bunch of dps that you will never be able to hold threat against? Seems to me a bit short sighted, they should have done that only for m+ at a certain point (like +5 onwards).