I think the original mission was to head to the sand village and investigate situation and lend assistance to the sand. I don't think Tsunade had the intention of sending Team Kakashi into Akatsuki's hide out to engage them. Otherwise, you would think she would send more than 3 jounin, 3 chuunin, and a gennin. But then you would also think that the Sand would send more than just a single old woman to rescue their own Kazekage.

I think Kishimoto is more concerned with making it interesting than making sense.