it's all plot!
It's not hard to understand, if sasuke died against him the story would be over. Naruto getting stronger and blablabla is all to bring Sasuke back but if Sasuke gets stopped (killed) by someone else, the story wouldn't go any further. Kishi made Bee go into 8 tails form because it's the only way he could have been defeated and gave the opportunity for Sasuke to awaken his Amaterasu.
Bee went into 8 tails to show them how strong he could be because they were annoying and asking for it. He wasn't aware of Sasuke amaterasu so he didn't know going into 8 tails form would turn out to be at his disadvantage. Going into 8 tails doesn't mean he was serious, Hachibi asked him why he went into this form and gave a stupid answer ( Raikage told him to not go into beast form often so he used the situation as an excuse to go into this form ). Bee tried to flee because it was a waste of time yet those fools kept asking for death believing they could win. Despite of that, he wanted to make them regret their decision by going into his strongest form. Bee later got owned by an unexpected jutsu but he didn't die or get paralyzed thus, team Taka failed the mission and the battle. I will mention this again, Bee loved to go into his 8 tails form but the Raikage didn't allow him to go into that form often or most likely never. Going into 8 tails is synonym of fun for bee, saying going into 8 tails form = being serious = you are stupid
End of the story, nor bee or taka won the battle.
Any fool that say team Taka won but failed the mission is ignorant. They captured a clone while the real one was still alive and able to move on it's own. It's like saying if one of Naruto's clone was captured = Naruto fails and lost the fight.
