Why i constantly keep dying to some unknown crap?!

This game is so badly designed in so many ways its getting annoying pretty quick.

You need full t16 map to get 1% exp, and then something unavoidable comes and bam dead (with great defences of course and 8.4k hp ffs).

I've just died to some elemental reflect map thou i dont deal elemental damage. WHY?!

Such crap happens constantly. Some unavoidable damage from god knows where just 1 shots no matter the defences. Whats the point of building them? Better to yolo full dps and just evaporate screens with some abracadabra class ffs.

Hard to know without seeing the actual map mods.

Any chance you got killed by your (Vaal) Molten Shell explosion? That deals ele damage and depending on your armour might be a factor.

Fairly sure it is the infernal cry combust. I have a recent thread talking about it. If you're at base xp go into reflect map to test, you will be fine until you pop infernal cry, then the combust will reflect you. Its not from the groundslam even though the exertion is being triggered by ground slam, so is not linked with brutality.

Molten shell should be fine, it is itself reflected damage which cant be reflected again.

https://www.pathofexile.com/forum/view-thread/3550703

Pretty sure it's what Belegur described. Killed me a few times aswell until I figured it out.

Looking at POB. It says your combust does 8-14k fire damage. Maybe can survive that on single target but if you hit a mob it's going to be bad.

Not 100% certain but what you are describing sounds a lot like what was happening to my slams. Nothing through the map then all of a sudden reflected. I don't use infernal cry in reflect maps now and don't get reflected. My combust does 80 to 130k fire damage and I only have 5k life, but also 90 max fire res. Sometimes would survive, but not against packs. So not certain it would one shot on your build, but if you think it was reflect that is most likely it.