One shots, long fights and overall Bossing design thoughts

So I was wondering - what is the best Boss fight in Poe2.
For me It is Jamanra during 1st campaign run of given league, slightly undergeared.
Why?
Because it is challenging. It takes good few minutes. It doesn't one shot unless i make a mistake of walking into double field (1st phase). Yet it is a demanding fight that usually lefts me with no potions.
That kind of fights are the best - Sweaty of dodging I emptied my defenses, but succeeded!


Now, why it is an issue to make it happen for the endgame?
1. Players sustain is never ending, so the only risk for the player that devs can apply is a one-shot.
2. Bosses that one-shot are making glass-cannon builds less risky, because Boss dies faster, and that makes one-shot risk less probable.

Summarizing the outcomes:
1. Player can go full offense for the fastest bossing and clear. Advantage of the clear speed is neutralizing the risks such build should struggle with - dying often.

2. Player can go full defense to be one-shot-proof. We've seen it is possible, but if game currently doesn't have broken damaging mechanic that has barely any investment, player pays the sturdyness in speed. Atm we have Atalui and other deviations that gives so much power, you can just go tank and still make it happen.

3. The balanced character - you invested into both, damage and defensives, like you "should". Now you die to one shots and have a long boss fight. It's the worst option.

How do we balance it out?
I would nerf players sustain and boss one-shots (so it one-shots only squishy and/or when player makes a mistake), also I would make Bosses tankier. Maybe add "potion reservation" for systems that have sustain elsewhere, so they don't overlap. Broken damaging systems out too obviously.

I know many of you wont like it, as for you the fun lies in epileptic zooming with no buttons and no dying. But I enjoy leaving sweaty after a boss fight.