I agree with some of your impressions and disagree with others, but just wanted to point out that Diablo II was also piss poor easy on Normal difficulty if you didn't use the PlayersX command to boost it to at least Players 4 and above.
Since DIII doesn't have that, it feels much easier, but it's pretty much on par. Normal is the "casual" mode so that those who don't want to invest too much time on the higher difficulties can finish the game.
There also seems to be a rather large jump in difficulty at each level, much more than it was on DII. I've read constant complains about Inferno being too unforgiving and too hard for solo characters.
Current PC Build
CPU - i7 8700K 3.7 GHz (4.7 GHz turbo) 6 cores OC'd to 5.2 GHz with Watercooling (Hydro Series H110i) | MB - Gigabyte Z370 HD3P ATX | Gigabyte GTX 1080ti Gaming OC BLACK 11G (1657 MHz Boost Core / 11010 MHz Memory) | RAM - Corsair DIMM 32GB DDR4, 2400 MHz | PSU - Corsair CX650M (80+ Bronze) 650W | Audio - Asus Essence STX II 7.1 | Monitor - Samsung U28E590D 4K UHD, Freesync, 1 ms, 60 Hz, 28"
