What is wrong with free champ rotation?

I feel like since the 14 champ per rotation change some thing got screwd. Why is Annie free again this week? She was in rotation last week. Why are Rengar and Kha never together anymore? Why some champions are much more often than others? I know it's not hard to implement in code some conditions or values to champs, and I'm sure Riot knows about it but "it's not on top of their priority list", but this changes would seriously took like 1-3 days to one programist to get done. I belive you can manage it Riot. Please fix it and get this overwith