While I wouldn’t mind more of a challenge for bosses especially in Hell difficulty, I can just imagine the surge of complaints about bosses being too hard… There were quite a few of them when the game was first released about Duriel. 
I think what is really needed is either a harder difficulty, or the ability to increase the difficulty in the game… Such as increasing the difficulty and density of monsters if you have the Standard of Heroes in your inventory, which I suggested in this thread. 