On the other end of the argument, if I'm heroic/mythic raiding and that's where I get (at least some) enjoyment from the game, having that series of accomplishments (in terms of gear) getting invalidated, or more realistically, diminished by having to chug through world quests that now take longer than they did previously (possibly on multiple toons, no less) doesn't feel good to me at all.
If they want to make WQs relevant they need to either keep pumping out new themes, or increasing the rewards - 860 is a step in the right direction, but for example, why do the world bosses still drop 860 as well? Shouldn't they also get that 20 level increase?
I mean, I understand the 'theoretical' argument of having things die so fast that people trying to tag can't get in on things, but while this is only based on my own personal evidence, I've never really had this problem aside from the occasional elite getting killed right before I get there, then having to wait a few minutes or server hop to find one where it's up.
If they tune things better I guess I can see it working okay, and that some of the hullabaloo is Blizz refusing to say anything beforehand (which seems to be a lot of the controversial decisions they make, at least as of late), but it definitely feels wonky right now.
That, and if they're so worried about scaling, they should maybe made it so there's approximately a 100 ilevel gap between fresh 800s and Mythic Nighthold raiders, with even more of a gap to come once Tomb releases.