Perhaps the subject isn't descriptive enough, but I've run into a couple of data polls where there has been a gap in some of our data, which often shows up as a blank space on a graph. Looking into this further, I saw data points reported to be 5 minutes apart, with the occasional data point 6 minutes out. Having done some custom monitor stuff with shell scripts in the past (a true horror, really) I think I know where this is coming from.
It seems as if Orion starts the poll, completes the poll, submits the data, then waits the defined interval before the next poll. However, since polls are not necessarily instant events, the poll cycle extends to the poll_time+interval. For example, if it takes 5 seconds to do a poll, the interval is really 5 minutes, 5 seconds.
My suggestion is to take the start time before the poll, do the poll, then wait for the remainder of the time before the next poll. The change might require some testing, but shouldn't be too difficult to implement.