Gao Guang wasn't good at scheming or business, but he was unbeatable in close combat.
The people at King's Defense weren't cut out to be assassins and didn't understand the assassin's craft, but they really knew how to fight a war.
If things went according to Shadowless's rhythm, the outcome was predictable, they'd be thoroughly defeated, since assassins wouldn't attack openly. They strike from the shadows, and Gao Guang's invincibility in close combat would be useless.
But give Shadowless a chance to make a move, perhaps a countermove to draw the snake from its hole, and create an opportunity for a face-to-face confrontation. Then, wouldn't there be a chance for a counterattack?
Typical warrior thinking: no matter how clever the tricks, I'll just go through with one move. If it works, it works; if not, so be it.