Of course, an achievement like that isn't meant to be easy. Some people in the thread suggest making it more like The Dedicated Few (so that not all the bosses have to be flawless in one run), but Bornakk says it's an achievement -- it's not required and if you really want to get the meaningless points, you'll just have to work around the disconnects. He's also shoring up discontent on the other side of things -- people are complaining that the Gonna Go When the Volcano Blows achievement is messing up their Sarth runs, because they're dodging insignificant damage rather than actually downing the boss. In fact, the easiest way to do that one is just to suicide in the very beginning (because the AoE can't hit corpses), and lots of people are doing that. Bornakk says change isn't likely -- the achievement is designed to be separate from gaining loot from the boss.
Bottom line on both of these is that they're achievements -- if they're hard or random or waste time, that's kind of the point. Blizzard may have caved on a few of the holiday achievements, but these endgame achievements aren't meant to be gotten easily or even without a little RNG help.