[Autumn]

there's a long term solution for fixing general tankiness involving limiting/capping physical/magical DR based on your armor types, though I don't know if that's necessarily entirely related to fixing this skill. (Though please do tell me if you'd like to hear about this in some other thread.)

Having it scale from CEL is just not good either, CEL giving physical DR basically makes it like an Evasion check and makes a defensive stat give a defensive stat, while I admit that CEL is just not a good stat to build outside of character theme at this current moment, it could create major problems in the future with building dodge and off tank, which is a widely popular thing and at that an annoying one.

Instead I'd rather have this passive give you Physical DR similar to Ogatas or Weathered body, one's that don't stack in the character screen, based on your sturm level, a balanced number for this would be Sturm*1.5 I think, either that or these passives just don't stack at all.