In the TV Show legends of tomorrow the Time Masters are introduced as some kind of time police and preserver of the time line. To do this, they must be able to detect changes to the timeline (before they affect them) and they must then travel to the time the change was made and revert it (or travel further back and prevent the change) or whatever.
In the show every second episode the main characters screw up the timeline and have to repair it. Gideon forecasts how the future would look like, if they don't. Shouldn't the screwed up timeline be noticed by the time masters of the future and shouldn't they do their job to pevent or revert the change? So why does not every time the main characters screw up the timeline a team of time masters appear and try to stop them? Do our main characters repair the damage before the time masters in the future can notice? Rip Hunter implies that if they cannot repair the timeline until a specific event occurs, the change will be permanent. If this is true and happens before the time masters in the future can notice, how are they supposed to do their job?
And by the way, if they are a police force (with fighting skills like Rip Hunter demonstrates) why do they send bounty hunters instead of - well - time masters?