Is there also a possibility that you share your gear, because from the sounds of it, dying to the small Hollows Heart spiders should not be possible these days, unless you are VERY undergeared.
On Cathdra Cliffs the AoE on not doing the mech also hits pretty hard, and can kill lower geared people.
Cold Storage should not hit hard, but as you said that you solo things, again if you are undergeared you propably just hit the enrage timer and die.
Heavens Mandate, idk, havnt done that in a while after it was buffed, only thing i can imagine is her World Breaker mech.
Sandstorm Temple should not wipe you (unless you hit the enrage time like on every boss) so its just healing up the damage u get.