Protection based damage reduction shouldmt be based on maximum health. Give it a balanced flat number in the equation.
Health pools are to small. 3-5k health should be common place.
Vitality is lame make it give you +10 health and protection of void poison necro
Hp regen needs to be based off maximum health
Potions need to restore % of maximum health
Think that sums up my view on hp. Ehp however is another topic and cant exclude @LizardIRL