Regeneration, recovery and recoup

we have 3 types of recoup: life, mana and "energy".

recoup works that some of our damage that we got is converted to life, mana or energy shield within 4 seconds

e.g. if we take 1000 damage and we have 50% recoup (life, mana and energy shield) we will get 125 (500/4) every second for 4 seconds life, mana and energy shield

but recoup is a pretty rare

in 3.21 we will be able to have 74% life recoup, 10% mana recoup and 0% energy shield recoup from the skill tree

from what I have learned life recoup can only be increased with life recovery but not with life regeneration, which makes recoup even more difficult to increase as there are only a few items not even skills what increase recovery

I don't know how recoup looks like with mana and energy shield but probably like with life i.e. increased regeneration doesn't do anything

I would like to build a character around recoup life/mana but at the moment it is and hard, expensive and inefficient and the only possible build at the moment is the ward loop which a few leagues ago got a nerf which caused a loss of perma ward from ~3k to 1.6k

in conclusion to make recoup life/mana or energy shield playable, as the main defensive style of play lacks the ability to increase recoup life/mana, energy shield through regeneration and recovery as there are only a few skills/items that increase these stats