When the sword essences were combined, his fighting strength greatly improved.
With the Fiery Wind Sword Essence, formed via the combination of Gale and Raging Fire, Jian Wushuang's fighting strength had improved immensely.
The increase in strength would be even greater if he could combine three sword essences.
As a conservative estimate, once Jian Wushuang combined three sword essences, his overall strength could be increased by at least three times!
However, it's pity, during the two years of meditation in the Sword Tomb, even though his comprehension of those four sword essences was at a high level, he was unable to combine three sword essences... Neither Sword Essences of Earth nor Waterdrop were combined with Fiery Wind Sword Essence successfully.
Successfully combining them depended on more than just comprehension. What he needed was a moment of insight.
If he was lucky, he could combine three sword essences in the next instant.