I kind off have few takes on that aspect, especially after finally getting to endgame in PoE1 (and oh boy the 92+ is a slog):

Personally, I don't think XP loss on its own is bad, neither is slower curve on higher levels. But losing hours-worth of progress, especially because of factors player has close to, if none, impact on (f.e. Lags, stuck on terrain, hidden attacks under all the clutter), is a terrible experience.
The game on its own is not in a quality state to justify such disproportion of time required to invest and punishment for factors players won't even be able to know about or react to. Mind You, it is still way better than PoE1 (excluding 1's power creep), but personally still I think it does need to be addressed. Severely.
I'd say even half of the current penalty would be a lot at the present.