I don't think you understand exactly what lengths Palpatine was willing to go to keep Anakin going down the path to the Dark Side. Ahsoka's death would push Anakin further down that path. This would also explain his desire for the ability to save people from death besides the death of his mother.
Dying in Order 66 would be fine, but she is close to Anakin and her death would serve the purpose that the Prequel Trilogy set forth- the fall of Anakin Skywalker.
I don't think that you understand the FACT that TCW is a kids TV show and killing off a primary character is most likely not gonna happen. Think about the season premier last week. The jedi who was killed was a nobody and they did not show her in the process of being killed (they focused on Maul's face), and they never showed her body (they focused on Obi Wan's face). Do you REALLY think the writers and animators could write a scene where Ahsoka is visibly killed in front of Anakin and for all viewers to witness? I think not.