I love the game as I did Diablo 3 and I currently play a Fire Sorcerer (Hydras). I progressed through the game in World tier 3 (where, in time, nothing seemed an issue - (Dungeons lev 20) to world tier 4 (Torment) where Dungeons lev 21 are too difficult . I know Diablo has a really loyal player base and many super skilled players but the game has to be playable and appeal to all standards of player. The progression from Lev 20 Nightmare dungeon to Lev 21 Torment dungeon simply cannot be an order of magnitude difference in difficulty. So I currently mill around in world tier 3 cos it’s the only place I’m enjoying the game (without getting one-shotted in dungeons). Sorry all it sounds like a rant but in fairness I love the game but a little embarassed gaining levels but not yet effective in world tier 4. Most other games have a smoother transition through the levels.
Hi
I remember when I transitioned from t3 to t4 and I had it the same: difficulty increased significantly, my gear was not adequate and I was one shotted when I was not careful enough. Tbh I just took it as challenge and actually enjoyed it because combat was bit more tactical, I had to be more careful and pay attention to what enemy is doing.
Instead of doing NMs I finished up all side quests I could find, did my renown and travelled open map a bit as it was more forgiving, than NMs. As power of my char and gear increased I then approached NM again.
My main is barb and I got lucky with good unique Overkill 2h weapon, that rolled with high stats early on T4. You are sorc so your experience might be different, but my brother is sorc too and I think he got to t4 and is doing pretty well from what he described taking on much higher NMs than his lvl.