Then I'd say that the advice in the post you quoted is valid: If you can't run Elite, run a lower difficulty. Despite the hyperbole, there are quests being run on a daily basis that not only aren't being run in Reaper, but aren't even being run on Elite, and that's through all three levels of play: Heroic, Epic and Legendary. I'm sure some of my guild mates could come here and state that there are people that are either looking to, or that actually are running Reaper. However, they can't say that if they're interested in running something we're discussing in guild that we won't drop to a difficulty where they feel comfortable running it. We keep players because we don't alienate them by excluding them from group activities, even when they, quite frankly, outright suck at the game/character building, etc.
It becomes more of an issue of "I won't run a lower difficulty because I shouldn't have to" than an issue with the game. All of these levels exist, and they exist because not everyone is ready, willing or able to run the higher difficulties. They exist because people look at class icons and believe that "x class can't contribute", but if someone wants to run "x class", they need to be able to. I found that link to the archived forums last night. It's amazing how, in 2008, ranged Rangers were being ostracized from groups because "their dps sucks". It's amazing how rogues "sucked at dps, coming through disabling all the traps but with only three kills". It's even more amazing to read posts like those from people that, today, insist that that wasn't going on back then.
So if anyone's really curious about what happened to grouping in this game, take a read through the forum's archives. I think you're in for an enlightening experience. You see, the developers didn't "break grouping", the players did. What's really ironic about reading some of those threads is how melee was king. If you come back closer to the present, you'll find that casters were king, and reading now, everyone must be ranged, which would include some casters. As an aside to this, the threads that I read predate Epic Destinies, so grouping in this game was on a downward spiral long before they were added.