Okay here is my suggestion. Please feel free to shoot me down, but I noticed that the dev's don't just respond to complaints. Some bosses could have been tougher, that was a given. Some bosses were insane and didn't need to be tougher. Here is what I suggest.
Tank swiper/ smashers;
These did not need a boost. With there self res ability they were tough enough as it was. When ever I fought one it seemed like they got back up 25% of the time at least. Roll back the hit point boost, roll back the acc to 15%, and up the self res %.
Crey Bosses;
Okay what was done here was insane. Fighting a force fielder with this many hp is just down right wrong, and I won't talk MOG, unstoppable, ect. This needs to be reversed completely. These guys were a fight before the change and are impossible now.
Others;
I understand the need to make the game more challenging but 40% was too much. Change it to 20/20% and keep the xp at 40%. Or if you insist on keeping it the same then at least up the xp to 60% to offset the debt that will be accrued accordingly.