I don't think there is enough information about groups, dungeons, or raids yet to make a judgement, maybe 85% of the time your role doesn't matter but in a certain dungeon or boss you'll need to change your make up? Alot of us are old and jaded when it comes to MMOs, you want a challenge but tedium shouldn't be the most challenging aspect of the game.
Wrangling cats isn't fun, having flexibility on the other hand gives you options and more importantly it gives the game designers options, if they know they can count on people having the ability to switch roles they can build around that, maybe no one wants to play a healer so you just try and DPS zerg a boss down via dodging attacks or interrupting attacks and if you are running a more traditional group maybe the boss will have a soft enrage timer or something that makes a tank/healer required if you don't DPS it down fast enough, it's all about choices. Now you could say you are forced to do what ever number crunchers tell you is the most optimal way to play but that's your choice, don't play what's fun, play what's best. We honestly don't know enough about the PvE to really say anything though, even the footage they showed just had mobs standing there because it's not very far along.
As for people saying go out and PUG someone to fill that last raid slot if someone can't make it, ask friends of friends, etc. You do know that 90% of the people are horrible right? Finding a DPS is easy, swing a dead cat, find a healer is harder, and finding a tank is nigh on impossible sometimes and hoping those people are good, well... Trying to find someone you want to group with is hard, very very hard. Back in the days of EQ the community was much small, much more hardcore so finding someone that wasn't a mouth breather was easier. Someone willing to wait on a list for a dungeon slot for hours is much different from people that log on to play for a hour or so after their kids have gone to bed.
