They make everything complicated and ranking up can be too easy/too hard with them...
Edit: Holy crap this got popular...
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On one of the screenshots of TTK there was the green XP levelling up bar at the bottom (I can't find the screenshot now sorry). So hopefully unlike the previous DLCs, we will have to level up the old fashion way for a while before light level kicks in again. I don't know exactly how this would work as if we remove our gear we would all drop down to level 20 again.