With fast-regen stamina, out of combat traps are going to be pointless
I don't see why traps should do anything to stamina in the first place. If stamina is to work as a sort of shield to health, representing character's active defences before the attacks fuck them up, then it stands to reason that attacks character couldn't have seen coming should bypass it altogether.
This means undetected traps and backstabs (is there backstab mechanics in game?).
Also particularly powerful attacks, and attacks by characters with much higher combat abilities should get chance to bypass stamina - or just make crits do so.