When does it say Vegeta's power level after he revives? And plus didn't they fight the Ginyu Force before Vegeta died? And didn't he have trouble with Jeice when they fought and Vegeta killed him? Plus technically Tien was in split form fighting Jeice and Burta so his power would be halved right and he still beat them.
And yea sure it didn't make sense seeing how they are again weak on Earth when Tien and Chiaotzu stayed on King Kai's planet until the Namek dragonballs were able to be used again so if that part had been actual canon and Tien trained even longer on Kai's planet he should have been a lot stronger then Vegeta...And how come they didn't get to learn the Kaioken? Sure Gokou stops using Kaioken cause of Super Saiyan but Tien and the rest would have been more valuable if they had learned Kaioken.
On second thought were they even said to be on Kai's planet in the manga?