Tsunade had to be protected herself by Naruto several times in that fight. And what do you mean that Orochimaru knew that Tsunade would try to kill him? What was the point of the whole meeting if he knew that? He hoped she's heal her arms, and in return he'd Edo Tensei her lover and brother. In the whole fight Orochimaru with Kabuto were pretty much all against everyone. He was able to kick their asses well, though he got beaten too. Orochimaru is the most powerful between them. But then again, Orochimaru hadn't had the opportunity to use his Ninjutsu, since he lost his arms. He was a massive threat to Tsunade with only his sword and some hand to hand combat.
Other than that fight, Tsunade got he ass kicked by Madara too easily. She's weaker than him, mainly because she's not the fighter type, rather than the medical ninja. You're a pretty much Tsunade fanboy, are't you? Or are you a girl?
.... =D