Good question @applepiie.

I use the basic principle that the output in the last 7 days need to be in-line with the 40-days moving average. I know this will not cover all situations but what is critical is that most systems receive sufficient work to create some decent competition resulting in a fair GRC distribution.

If you take Sourcefinder@home for example, it is almost impossbile to catch a WU. It is more a lucky draw with the winner receiving around 1 GRC per returned WU at the moment. In an other article (here) on Steemit I describes this further.