Fabian, you have found one of my old problems. There is a request on Bugzilla to store bot edits in a table other than recent changes in order to be able to sort them out of page histories. As the others wrote, this is a very complicated question with few hope to get exact results, but please let me know if you have some acceptable solution.
2012/5/26 Platonides Platonides@gmail.com
As a bot account should not perform any "manual" activity, that's a pretty good indicator.
Even this is not 100% true. I sometimes use my bot for mass text replacements witihin one article as this is the cheapest way but this is intended to be a single edit while I am working on that page manually.