Have I repped you for that Manson sig yet? if not Im doing it now anyway lol. And think of it this way, Tsunade's fighting style is brutally straight-forward, she isnt exceptionally fast and often leaves herself open to quicker oponents when she attacks, would it not help a lot to have a partner who can pin your opponents down with sand for you to hit them?
Likewise I think tsunade would benefit greatly from having a mobile sand defense around her while attacking, Gaara is capable of shielding a large area from attacks and shield his own body too while staying on the offensive all at the same time. with Tsunade boosting his chakra and healing him, they could keep it up indefinitely. this is without talking about either of their acctualy "techniques".
