Max Health calculations are extremely messed up. Swapping 1 item may result in getting much lower health than intended.
I have around 30 k health (I really cannot be sure how much it should be), and taking 1 piece off and putting it back on, I usually end up with something around 28 k. If I take out ALL my equipment, based on the last few items I believe, I get 22 k (if I take off others, I have around 7k though.) And if I decide put only the chest piece that gives 2300ish health back on, on top of that 22k, my health pool is 'boosted` up to something a little under 23k. (I have 140% increased health or so from the passive tree)

I love trying out builds in such games, but the amount of bugs and the majority of skill tree not working make it impossible to enjoy the game at all.