Some suggestions

[Addah]

Nightmare XP
Yes it's very easy to reach level 95 after a day or two if you know how, but new players who aren't familiar get stuck pretty easy without having friends or asking people for help. It's an inconvenience for them with this enhanced difficulty, depending on timezones or the hours they play there may not be others around willing to help.

The balance with inferno cows on nightmare vs hell would be sacrificing drop rates to gain XP rates if you can't possibly kill hell content as a new player. End-game and level 99 players wouldn't waste their time on Nightmare inferno cows unless they're helping purely for friends to level up.

Azathoth Organs
The organ drop rates are not equal, I've done dozens of hell cows with 14 mules and 90% of Azathoth organ drops are brains/hearts/eyes, I have full inventory/stash of them and almost 0 tails/horns. Yes luck does factor in but if you farm enough you'll see a clear difference in the drop rate.

Runewords
Yeah perhaps, just an idea to keep people spending/buying runes.