I already answered that a looong time ago, so here are a few of my previous posts for a detailed answer:
Also there is another thread discussing this:
TL:DR
I think a healthy death penalty for exp can achieve good things.
It makes achieving maximum level more meaningful and also gives combat another new dynamic.
Most important though is, that it doesn’t gate any builds.
So a good scaling of that death penalty over the level curve is very important.
The last few levels should really just be for min-maxing and it should feel like required to achieve these last few level ups.
EDIT: Another thing that is also pretty important, that Mike on the Dev stream also recently touched on:
People need to realize, that it’s not necessarily expected to reach level 100.
It is OK to not be max level. And he said that they might possibly even stretch out lvl 100 further, so that it takes even longer to reach.
This is not an MMO, where a big chunk of content is locked behind some arbitrary level number.
The last levels are and should be an achievement.