L
L3mmi05/Val
In the current state of the game, stubborn heavily dominates the meta.
I don't think I have to go too in depth on why, it's been said a lot; but to make it short:
In my opinion, the two issues are
  1. Ignores knockback, and with it half the gameplay on ring
  2. Basically acts as a permanent -1 damage in higher tempo play, which becomes even more problematic when combined with adamant.
My suggestion is a radical rework; instead of reducing damage by 1, effectively rewarding you for dashing head on into structures, we make the dash faster, longer* and immune to knockback, but you take one MORE damage if you get hit by dashing.
This would let it retain it's place as a really aggressive, rush stone, but reward weaving through your opponent's attacks at high speed instead of just tanking them, while still leaving the option open to avoid a ring-out or close that last bit of distance at the cost of hp.
That way, stubborn would turn into a calculated tradeoff that you have to think about using (like most other stones) instead of making "dash into the incoming structure" the best option in a lot of cases.
*I'm not sure if a longer dash would actually be good, let me know what yall think