Dual Blade's Tornado Spin

Hello.

I'm wondering if tornado spin is really necessary for DB. I'm already used of doing Flying Assaulter + bloody storm combo, and i don't see the point in buying the CS skill book, since theres no skill book for sale in broa.

I want opnion from others, if FA + TS is better than FA + BS.

I feel like just maxing out my other skills and leaving TS at lvl 5, since FA+BS is pure ownage