Some games have a mechanic where when the disparity between the player and the monster is too great, that no exp is rewarded. Or some threshold where the exp rewarded is such a small percentage of that needed to be level, that it would take hundreds of hours kill rats or baby goblins to advance. That mechanism seems effective for sending people along to greener pastures.
Never stopped me in WOW from killing 20 humanoids at a time to farm low level cloth en masse.
Never stopped any of the thousands of gold farmers and bots either.
In this case the XP is totally irrelevant.
It's hard to explain exactly what I'd like to see get built without writing a book on it.
In a game balanced around hardcore mode XP will be easier to come by because players are constantly dying.
The farming is a good point I did that in Asheron's Call way back in the day. Asheron's Call had the best loot system of any game I've ever played. The loot was level appropriate but it was random within ranges, so it could generate all kinds of neat stuff.
You've got your potential PHD Dissertation "HARDCORE MODE: PWNED NOOBS"
Hardcore mode is only unforgiving on other games because no other game is designed for hardcore mode to be the standard. None that I know of anyway. Although as I have already alluded to here the entire Roguelike/Roguelite genre seems to be the exception.
So what I'm envisioning is more of a turn-based roguelike MMO with a big economy linked to crypto.