I read it in the forum:
The "Valiant Warrior" set bonus is currently bugged. As mentioned above, the set is suppose to give a 25% chance to reduce enemy defense by 450 and increase player defense by 450. Instead, when the set bonus triggers, the player does millions of points of damage to the enemy. Furthermore, any ally that hits the same enemy will also do millions of points of damage. An additional bug is that the affected enemy will do millions of points of damage to the player (guardian fighter) causing a one-shot.
Happy farming
Quelle
I wonder why they dont delete the post.