Board Thread:Naruto Discussions/@comment-26104757-20150617022803/@comment-26518343-20150629143439

Might be overthinking it a little. Shizune really has very little to do with people who were working under Orochimaru and Jiraiya.

I just assumed Shizune was an "apprentice" of Tsunade because she wasn't skilled enough in combat to go on missions regularly. Same as Iruka working in the Academy because he wasn't good enough in combat to be doing missions all the time or Izumo & Kotetsu guarding the gates of the Leaf Village instead of being on missions every day.

In Sakura's case, she went to Tsunade first because she wasn't on the level of her teammates and was looking for a way to catch up.