Bring back deleveling in 2.0

[Mudd]

Because deleveling is so scary, right.

In a sense. Imagine if you die while fighting Ifrit at cap. You would Delevel if you lost.
What deleving encourages is more thought before a fight. More Precaution.
It also discourages zerg rushing enemies with complete disregard, though this was more of a problem when parties were 15 man.
For those of you who dont know, you only lose exp if you don't get a raise)

I might be misunderstanding which game you're talking about, but in FFXI, raise only returned a percentage of EXP back, depending on the tier.