I'd just like to mention that so far, each Raid has been an improvement in terms of difficulty. I think with Asation NM we'll see another level building on top of Explosive Conflict NM which most probably will wield next tier gear (65). They started very easy and are now on a level where (I hope) they have enough experience to give some interesting and challenging content.
I understand that people tend to want more bosses, however if I rembember for example in EQ2 Veeshans Peak with 3 wings for a total of around 10 bosses... only 2 bosses were a real challenge. Nexona and Silverwing from which Nexona was harder (having the hardest boss in the first of three wings... was not very popular). As I didn't play WoW, I'm not familiar how the difficulty is increasing / if you can choose to do one mob before the other one or vice versa... but at least I don't have locked content where as bosses would be so bugged so they'd be unbeatable or locked as in "locked" and to be released at some point in the future.
Another big plus for me is the smaller amount of people required (EQ2 had 12/ 24man raids) but with it comes more responsibility for each person.