Im assuming items are identical.
The level 80 barely beating tier 60 nightmare dungeons. Should the level 100 be clearing nmd 80s then or also only lvl 60 nmds?
Are you only questioning the raw stats for being X level, or are you including the difference in having another 80 paragon points, new whole boards, more glyphs, etc?
paragon points damage goes up multiplicative, not additive
The difference is substantial. As the gap between your level and the creative level shrinks they do less damage to you and you do more damage to them. Even if you never change gear just the paragon points alone make a huge difference.
Paragon Board aside, even just the level difference has an inpact?
So fighting Uber Duriel at lvl 75 would be harder than at lvl 90 even with same gear and unused paragon points?
It feels that way and it probably is that way.
Call it "level bias’, “level mitigation”, pretty much every game that progresses though a leveling system has this implemented at least on some degree.
Base life and core stats increase by level. You have a smaller health pool and a bit less damage at 75 vs. 90. All your scaling is off base damage, which increases with core stats.