I believe things will all workout in Heroes, Inc. People will hit the level cap and run instances with other people, these things tend to happen in an MMO. Some people may have to spec differently for a while (like me probably going resto).
I understand the goals in Heroes are focused more on the "journey" and not the end of the line, more on community than min/maxing a raid to conquer a particular encounter. All of that is fine, its great, in fact I would not want it any other way.
With that said, some people have expectations that are very very streamlined and in my opinion unrealistic. Wanting a group for every quest and every xp point is the same for me as others have issues with "hand holding" in instances. I like the challenge of busting out levels, sure I read the major storyline, I follow the quests. But I like grouping, and in my opinion the real grouping truly starts at 80.
One issue with me is the whole "instance challenge" situation. I understand wanting a challenging encounter. And trust me, at this stage and the forseeable future, EVERY other heroic boss is a definite challenge regardless of who is in the group. Most of the achievements in heroics are very challenging, in fact some are outright ridiculous and will require months of raiding to get properly geared to complete them. If it is a challenge that is being sought, believe me, for a casual guild like Heroes it could take 8 months to a YEAR, yes a year to get them done.
I will say this, I am very excited to group with all of heroes. I even plan on speccing resto so I can get in as many groups with my friends as possible.
As for raiding, I believe Lakini is exactly right, no matter when raiding starts, stops, blows up, vanishes, or whatever, not everyone will be happy. Bottom line as I see it, no one is in a ridiculous rush to get into Naxx, but everyone is ready and excited to group together! See ya in-game.