I was thinking about the idea of letting heroes use Hope to somehow reduce damage. My idea is to use a point of Hope to reduce an enemy (attack) success level by one step, but not below a single success.
So the damage is reduced, but never eliminated.

What do you think about this?

That sounds like quite a good idea... although it could make combat considerably less risky. For me, and my friends, the brutality of combat is what makes it different from other RPGs, such as Dungeons and Dragons, something they all enjoy playing. in TOR, the fact that there is always a chance to become completely killed in one blow is always a good insentive to be sensible in battle, and I feel that if one could reduce the damage dealt by an attack, combat would become a combination of squashing enemies and spamming Hope points

There is already/also the Knockback rule.