If I were to buff Dorans shield I would rework the passive and remove the health regen
New Unique passive: Every second out of combat after being out of combat for 3 seconds you generate 5 block, cap of 100 block. Whenever a single target ability or auto attack hits you, points of block are used to negate 50% of the damage, consuming each point of block for each amount of damage negated. If at 100 block and the attack would do more than all 100 block, it only reduces the damage by 100.