Absolutely worth using Chinese infantry on the offense but do not over commit. Your goal as China is to kill as many Japanese units as possible, and to push back as much as possible. Even 1 on 1 duels can be worth it at times. A lone infantry against a Japanese infantry kills 40% of the time vs. 33% of the time on defense. You may also take some income back and slow down the Japanese.
You have to figure out what you can afford to use vs. critical objectives, e.g., holding Yunnan, making it very costly to retake Yunnan, or ensuring the survival of your fighter / ensuring that retaking Yunnan is possible.