Yet Tsunade has stayed away from the battle and used her chakra to heal from afar. I seriously doubt she's going to get much better.
And we've also got nobody talking about how powerful she us except in medical ninjutsu. Jiraiya has had people call him powerful. He also trained while out and about while Tsunade lost all her money gambling instead.
As for Deidara..why in the world would he train one eye to try and defeat Itachi with when he usually keeps it covered anyway?