My Theory

My theory is that if Tien wasn't in the series, then the Z-Fighters would all be dead. On Namek, Krillin used the Solar Flare to get away from Dodoria. If he hadn't, then Dodoria would have killed him, Gohan, and Dende and they wouldn't make the wishes. Also, Goku wouldn't see Krillin die and he wouldn't go Super Saiyan. He would be destroyed by Frieza.

In the Frieza saga, Krillin distracts Frieza to give Dende enough time to heal Gohan. To escape him, Krillin uses a Solar Flare.

When battling Imperfect Cell, Krillin would have been absorbed if he hadn't used the Solar Flare. Also, Tien kept Cell busy and gave 18 and 16 enough time to get away. Though, Vegeta ruined it by letting Cell absorb her. Later in the series, Tien saves Hercule and Dende's life. If Dende was killed, they wouldn't have been able to wish back everyone killed by Buu.

In the other world tournament, Goku faces a fighter that turns the ring into a water. Goku uses the Solar Flare to get away from him and out of the water. He then uses the Kamehameha to win. If he hadn't used the Solar Flare, he would have lost, and might not have been able to return to Earth for the World Martial Arts Tournament and save the world again.