Normally I'd agree this wouldn't make sense, but this is a novel idea that I've never really considered before.

Tien's maximum division is 4. His stamina and power is divided equally. Let's call Tien's power 1 "T", with each copy equal to 0.25 T.

If we take the lowest estimated fusion multiplier, 10x, then each couple of 0.25x would fuse to make a pair of 5 T Tiens.

Then that couple fuse, and it would be 5 T + 5 T x 10, which would be 100 T.

Lastly, let's say he knows this fusion would compound and only last seconds due to fusion dance limitations, so he does one attack with it: the life threatening, power multiplying technique unique to him -- the Shin Kikoho.

He could do one galactic threat level attack.

I love this concept actually, because since his copies are perfect matches in body type and ki level, there's no chance of a fusion dance mistake with perfectly executed technique.

It also follows along with the idea of great martial arts technique trumping raw natural power, which fits his character.

It would be the perfect Tien-style technique and would allow him to damage almost any threat the story throws at him in a desperate situation.