Is Sasuke's Sharingan Ever Useful?

I'm just not seeing how Sasuke's Sharingan could ever be useful, and it actually looks like using it lowers your overall attack output.

Sharingan can only give Sasuke 3 actual turns of attack boost since the other 7 turns are consumed by other unit's turns. Also, you have to wait 4 turns after using Sharingan to have enough Chakra to use Fire Ball Jutsu, so you can't use Fire Ball Jutsu in combination with Sharingan.

Here's the comparison of his attack over 4 turns when he uses Sharingan vs. using his Chakra to use Fire Ball Jutsu twice:

| 1st Turn | 2nd Turn| 3rd Turn| 4th Turn| Total ---|---|----|----|----|---- Using Sharingan| 0% (Used Sharingan)| 150% (Normal Attack)| 150% (Normal Attack)| 150% (Normal Attack)| =450% Using Fire Ball Jutsu and normal attacks| 180% (Fire Ball Jutsu)| 180% (Fire Ball Jutsu)| 100% (Normal Attack)| 100% (Normal Attack)| =560%

Keep in mind that each Fire Ball Jutsu has a much larger range than Sasuke's normal attack range.

Unless I'm missing something, it looks like using Sharingan actually makes Sasuke worse.