Yaaa, if tsunade is out of the question than Kabuto hands down,
Shizune^
Yeah but Kabuto is much better, Tsunade even says that he is the best she has ever seen.
I don't know how she would know that but she said it in the fight between them in Part 1. Kabuto did experiments all the time to help Oro. He doesn't really heal people though since Oro is gone, he just kills them and uses his medical expertise to experiment and make clones and stuff.
1) Kabuto
2) Shizune
3) Sakura (or Ino)
4) Ino (or Sakura)