I remember before Ulduar came out, there were alot of blue posts about the difficulty difference between naxx and ulduar.Each new tier is suppost to be harder then the last. But I have not seen anything on the
difficulty of the new raids. From what i have been reading about the PTRs. Most guilds are blowing thru the 1st bosses no problem. But you cant really go by that becuase they may get buffs or nerfs by the time it is
released.