Yeah.....I'm not sure what Phazael and his wife are dying to, but getting one-shot doesn't really happen before T4 unless I guess you are just super casual and not optimised at all, i.e. just throwing on random gear and going at it.
Season 0 my sorc was getting one-shotted AFTER the latest patch, and only T4, mainly in NM 30+ dungeons. That shit is pure ridiculous.
But prior to that, my sorc would get super low on hps from like the corpse bow and shit, but never 1-shot.
Currently lvl 54 on necro, minion build of my own design, and so far smooth sailing, the new gems make it SUPER casual lol, like I dont even have to push buttons. Using the two new gems, the one that auto-casts and the decrepify one, I just run around and let my pets do their thing. Just have to stand close, cast bone storm, get the aspect that fortifies you as bone storm does damage, get the other aspect that prolongs your bone storm by using corpses....like you can't die. If I can optimize it to get it so I can have bone storm up all the time.....woo boy.
Not sure about continuing after Season 1 though, or until I play each class. I'm just not the kind of person that enjoys rerolling new characters every season, I would prefer having one character that just gets stronger (games like Destiny, Call of Duty, The Division, etc). I have a feeling I'm only enjoying it currently because I haven't played a necro before, and once these OP gems go away, I'm not gonna ever want to roll another necro. So unless they make compelling content for the Eternal realm (unlikely, since they want to monetize the game through Seasons), then eventually I'm gonna run out of things to do.