Is it me or has the loot table dropped. Why is it that I am getting far more 3 star greys in the last boss fight of brutal, or any boss fight for that matter. And honestly why am I still getting 3 star greys in Nightmare?

Isn't the idea of progressing through more difficult content that you receive better loot?

I would hope that by the time you are trudging through nightmare paying 16 energy per fight you are getting at least 5 star greys, or 4 star blues. Not the same stuff you are getting in the first and second levels of difficulty.

Also with potions, what's the incentive in fighting level 120 and above bosses to get one small potion. These things should be tiered. Lower level bosses, small  potions, mid level bosses, mid potions, top level bosses, big potions.

But I am convinced that they changed something about the loot table to force people into nightmare, which still yields the same low level gear. So again no reward. Unless you are buying gear.

I think in time will get sick of that. You want to progress and feel like you are getting better stuff as you fight harder content.