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We have smoothed out level progression from 50-60. This should
mitigate the "penalty effect" that occurs in levels 51, 54 and 59. Note
that it will cost the same experience to level from 50 to 60 as it did
before. Also, death experience loss will appear different in some
levels. This is an unfortunate side effect that must remain to prevent
some experience exploits.
Yeah, I definitely remember them doing this change, but that was only to smooth out hell level differences, not remove them completely. Basically, 51, 54 and 59 were hell levels for hell levels lol. So, they just spread out the hell level exp from 51 - 59 so it was exactly the same amount of exp, just not jumps at any particular level. Prior to this change, level 59 was an insanely long hell level. After the change, it wasn't too bad.
Unless they have made other changes since these, the hell levels should still exist. Though, it sounds like they probably removed the ones below level 51. As far as I can tell, 51-59 are still hell levels on Live. Though, with level 85 being the cap atm, it doesn't really make sense to have hell levels in the middle and none after.