tl;dr everything
Aside from them adjusting T4 mob, What did SE nerf? I don't recall anything getting a nerf. We do have an Echo Buff, Which is Optional. So if content is to easy for you and your friends TURN OFF THE ECHO BUFF! SE isn't forcing players to use it.

Quote Originally Posted by MasamuneBranford View Post
To many, nerfed content is not fun. It's not fun playing the final two 2.0 storyline dungeons and seeing I-level 100 players slaughtering the end boss within seconds. It's not fun fighting boss battles with a 50% to 25% echo buff (it's also not realistic to expect others in a group to turn the buff off)..
Did you think that SE was going to make the two last story dungeons harder every patch? If its not fun don't use it, Simple turn off the buff. At least with an optional buff players can still experience the difficulty vs a flat out Nerf, Where no one gets a choice. How many players have beaten T5/Titan EX because of the buff? And there are still Thousands of players that can't beat t5/Titan EX even with buffs. So its either Nerf or a Buff, A buff is basically like giving you extra ilvls in gear and still requires skills to beat the content. Where as a Nerf you could just over gear and faceroll boss mechanics. No one wants to be stuck doing the same content for 3-6 months, Wheres the fun in that? If you can do the content without a buff, That's great. But there are a lot more people who cannot, So that makes them the majority.