I am happy that bosses in T2-T3-T4 did get a bit of a difficulty to them. They require a proper char with good gear. I am all for hard bosses.
That being said, when you up the difficulty then class/build balance becomes astronomically more important. If the best builds, say top 3 builds in the game gets a challenge then the rest of your classes/builds are just dead.
It is VERY VERY important that there is some sort of a balance between classes. If a Necro with good gear takes 1 minute to kill a T4 boss. What happens now is that an equally geared sorc will take 50 minutes to kill that same boss. And yes there absolutely is a 50x damage on Necro compared to Sorc. Just as an example.
I hope, and they should do a big balance patch in the first week or two.