[Joseph Jostar]

I personally think that being able to mutate 10* armors to start with wasn't the greatest idea, but more on-subject I feel like the DR-stacking is much more of an issue than kip-up (though that's still a bit silly). Like you demonstrated, maining martial artist gives unarmored Turtle Shell users as a whole a ridiculous amount of DR (nearly 40-50% without spending a SINGLE POINT in Defense, if it stacks additively, and still ~35-40% if it stacks multiplicatively!)

To be perfectly honest, Turtle Shell might not even be the issue so much as just how MUCH DR is available and the fact that all of it stacks. Much like how people were stacking the passives from Boxer and MG to become nigh-immune to physical damage before they got made into 'defensive knowledge' skills.