[Shujin]

Maybe because they are still stupidly strong with one of the strongest burst damage attacks that doesn´t even need any stats aslong as you can hit and have some HP and there is no reason why they should sustain all damage what so ever just for the "Theme" when the theme is still there. They are harder to put down then others, they get stronger the lower their HP gets. Swordmaster Ring needs 2 solts, technically, since you must have a sword.
But thats beside the point.

It´s like saying BoI should get a damage thereshold for reducing it´s level so multi hits don´t ruin it. But thats the whole point behind it.

Fights are often decided by this one attack they sustain, they really don´t need a free card for everything for one turn. It still combineable with other things like Cobra/BoI Blade barrier or what have you.
Again, I rather see the other skills, mostly painproof cause that skill is really bad at the moment, get something for their theme. Maybe even something you say here,aslong painproof is active?
That would be okay.