Difficulty of normal content.

[jdtuggey]

...that damage always 1 shots you.

The bosses are:
MaulSkull from Skydeep Cenote
Antivirus from Alexandria
And the champion that took me an hour to defeat The Herpe master, "Herpekaris" from Origenics. This boss almost made me quit the game...

Except only Maulskull has a one shot mechanic, and once you get caught by it, you're supposed to be prepared when the next knockback comes ?
If you were getting one shot by things other than getting knocked off a platform, maybe there's a problem somewhere that isn't related to the content or your performance, like trailing behind on gear ?
I've been playing a lot of viper myself, and nothing has one shot me, and I level through dungeons and I got hit plenty by these mechanics.
Another think that's important about playing melee classes: You have immense survivability, I think you might be ignoring Second Wind and Bloodbath ?
Man, I can tank wall to wall pulls with these while healers rez flattened tanks. I couldn't tank a whole pull all the way through but you can heal yourself quite a bit.
Concerning getting hit while following the scions, yeah, latency would do that, you're always a bit behind on time to the server.
You should learn from them, not depend on them. That means looking at what they do so you can do it yourself next time, without following them.

Also don't rely on the VFX effects. If you're in the telegraph (orange zone) when it disappears, you're gonna get hit 2.5 secs later when it resolves, no matter if you're not in the telegraph once that 2.5 secs has passed.
I say this because both bosses that aren't maulskull have like, a phase where they do a series of AoE patterns.
For Herpekaris, you need to get into his face and look at which arm he lifts, you go on the other side just beyond the edge of the target circle, and you're clear.
For antivirus, you need to follow the pattern that appears, it resolves in the same order, you need to get in when it's a circle, you need to avoid getting in and avoid the beams that come out when it's a cross.
Gotta go zoom, so you need to prepare for it and think about what you're gonna do ahead of time. Ignore the immune reaction casts, if you're fast enough following the patterns, you always end up getting out of it in the nick of time. Soon as the telegraph is gone, you can move. Doesn't matter if a nuke blows in your face, as long as you weren't in its telegraph when it disappeared. This is the other side of the medal concerning what I said about not relying on VFX effects.

Concerning tanks surviving more.... It's the premise of their job, lol, if the hat suits you, enjoy it mate. ♥
I play all roles and dps does feel like the hardest role by far to me, but the game also isn't hard from my perspective at this level of content, no matter what role.