Shifter healing heals 2 injuries, not all of them. The left part of the defense skill tree is bad, damage reduction in this game is exponential, hp is linear, so go for hp, if you need hardy counter you're just bad.
If you have shifter regen right side defense tree is bad, since regen heals a set amount, not a % every hitpoint is more valuable, so losing less per hit with defense is more beneficial, same story for bandages. Abilities that heal a % benefit more from a bigger health pool like potato, or titan shifting
i think reiss is built for shifter raids because you dont need to fill up the ber so protecting and beating eren is hella easy so thats why i want reiss (and i already have fritz)