BM users and the lack of defensive mitigation nods

Something I don t clearly understand is Why Mana users have so much defensive options (MOM,AA,Mana gained when hit, mana taken before life,ability to take hudge amount of life too) while BM keystone users can t have things like a AA or a MOM to use.

I realized that it is much harder to get 800+ life regen as a defensive BM user than having 3000 Mana+Mom+AA for a mana user.

Even with High regen, a BM users have trouble because of is life being reserved, making high survivability+ having dps almost impossible in most situation when Mana users can in general Have nice life pool and great defensive options and having a great diversity of builds.

Related to this, why when you take Eldritch battery, all your ES is converted to Mana but when you take BM keystone, your mana pool is not at least partialy transferred to your blood pool.

In past, Vaal pact could have been used to help BM keystone users but with the new change, You need so much life leech its make you build very gear dependent and expensive compared to Mana users.

something like MOM but adapted to BM keystone would be nice.

Some damages deduced from life regen maybe?

Something unrelated, Why is wall of thorns keystone so far away from the marauder? seems to me the marauder strength type fit more the tank reflect stereotype than the shadow or ranger.