Stuck with DW Sunder Glad

Hi exiles!

I feel stuck on my char. Currently playing a DW Sunder Gladiator in harbinger league (named "diMalatesta"). I'm at lvl 70 roughly.

I wasn't able to finish act 10 Boss or lvl 68 trial on my own. It often feels like no dmg comes in at all and then there is this famous one-hit. I can't even tell you what's happening in these moments, if I suffer a elemental alignment or failed movement on an attack or whatever.

Anyway, currency is low and I finished the endboss in a group with a necromancer. No effing problem at all. Felt like I did way more dmg than he/her did and didn't ever drop significantly. Started mapping, but it still was the same feeling. I breath through the maps until there is one pack/boss that one-hits me. Packs may had reflect, crit or dmg mod I can't tell. I just respawned and rolled over them. Some bosses still hurt, like a lot. They simply onehittet or nearly onehittet me and I had no flask charges left, so I died slowly.

Basically, what to do?

I would prefer to change something on my own. Of course I could ask a friend to push me through lab for 3rd ascendancy, leading to a bit of block. Of course I could try to remove some dmg skills and rise hp pool for more life leech. But I guess I missed something totally here, I am just to blind to see it.

Thx in advance.

so many things.

- upgrade your axe. there're many upgrades for 1c or lesser on poe.trade

- your gems are all over the place. why convocation? why vitality?
put your aura gems into a weapon slot and keep it there.
you'll need to recolour some of your gear

- spend 1 point at the Vitality Void cluster to get 0.4% mana leech, so you can replace your belt with something better. more res, more life.

- empty sockets in your gloves. get a golem, either flame for more dps, or stone for regen (that replaces your need for vitality)

- auras. herald of ash + hatred is the standard offensive setup. defensive setups will be blasphemy+enfeeble/temporal chain and Artic Armour. decide if you need more offence or more defence.

- link your warchief in your gloves for 4L. AW + melee physical + faster attacks + conc eff / ruthless / maim / chance to bleed / added fire damage

- you're generating endurance and frenzy charges from your ascendancy. you'll have to decide if you want to save your endurance charges in fights, or expand them with Immortal Call. that'll decide your CWDT setup.

expand your endurance charges: CWDT + immortal call + increased duration + molten shell (optional)

don't want to expand your endurance charges: CWDT + vortex + 2 other gems
options include:
1. molten shell
2. blade vortex + blind
3. blade vortex + knockback
4. blade vortex + life gain on hit

other CWDT setup:
https://www.reddit.com/r/pathofexile/comments/66a2h4/list_of_useful_cwdt_setups_did_i_miss_any/

you need to change your flasks.

one for bleed removal
one for ignite removal
aim for:
(bubbling) or (seething) flask of (staunching) AND (dousing)

a basalt flask might be better than a granite for phy dmg mitigation

1 last thing. Sunder does not attack with off-hand AT ALL. unless you're thinking of Cleave instead? if you wanna DW with sunder, your off hand will be Scaeva with red/green sockets instead
EDIT: Temperous steel and Scaeva is both used as a stat-stick for sunder. there're advocates for both weapons, which i can't advise you on.

All in all, you have alot of work to do to salvage your character.