Even with Battle of Gods, I don't know about that reference of Vegeta's brother, because Vegeta says that Goku and Gohan were the last Saiyans. Maybe he said that because he's a wussy, and didn't consider his brother a Saiyan, but Freeza wasn't aware of any others, which if he was of Saiyan royalty, I think he'd know of Tarble.
They got my money and will continue to if they make more! The only one I didn't like was Fusion Reborn. They're fun! I really like the Garlic saga too, despite the contradictions with Gohan and Goku meeting Krillin for the first time, the revelation of Gohan's hidden power, and the reason Krillin risked the world by not killing Android 18, because it was the first girl that showed affection to him, when he already had Maron. In my opinion, he would have sacrificed 18 to kill Cell, and wished her back with the Dragon Balls, but throughout the series, one of his main goals was to get a girlfriend and that's why he froze with 18. I think it would have better as movie sequel to Dead Zone.