I was playing with it on my brother's account (I was grinding for him) and it's the only mythical torso he has. So naturally I tell him to play it. However it's just flat out bad. Auto loss to resistance pads, health is way too low, OR resistance is too low. One can argue both are really. it needs 200 - 250 health if it's gonna only have 20 resistance. Battles are very fast now, 20 resistance is nothing, and every heat/physical mech you face will drain that pathetic resistance. Diamond shell is the worst torso hands down. Galaxus model A might be a better alternative.
This item may need to be completely redone. Better stats wouldn't hurt.
I don't mind helping in redesigning (because I want it to be done right, and the devs can't seem to do that). I can crunch some numbers and tell you an adequate amount of resistance and health (and even stats may be moved around). Of course I wont waste my time if it wont be implemented.