I die a lot even at level 100. I think a lot of survivability comes from hitstun, as in just making contact before monsters do. Even if you're not oneshotting things, if you can make an effort to roll at and hit anything before it reacts to you. I'm nearly unkillable and facetank basically everything with 88% evasion (so cheap) but I still die plenty. Authentic act of touching first basically ensures the kill. Sure act 1 their head bobs and they cast and ya thats an opportunity to die. At your level, they'll die before their hitstun wears off. So prioritize that. Magnified area if you need it. Just make dang contact first.
I think main deal if you want to progress: find a way to not give a shit about dying. Also buy omens of amelioration. Fat stacks. Always have one active, but also: you can only pop one per instance. So if you die a bunch in a map or temple, that omen will only work the first time. Just be easy and take things slower is always always always a good bet if your weapon won't carry you through content. Which leads to the next point: what's your glove/jewelry/weapon looking like? Great starts, upgrade the worst one first.
Hmu if you need those omens I'll buy you a few stacks
Also also: I skipped through some of your post and only replied to the title: I league started that build! Hell yeah you can die. Melee is difficult but it kind of really gels if you can kinda finesse dodge rolling, a VERY short sprint, into whirling assault, into roll/sprint again, there's a weird cadence to it that you gotta just master, but if you can time that last little bit of invulnerability at the end of your sprint with the startup of whirling assault, you can basically spin yourself through a whole map. Having a reallllly nice staff helps too. I'm happy to gift some things but I also don't want to spoil your journey.