The problem I have with these statistics is that there is a strong bias towards countries where there are more competitions.
Well I do not think you can use statistics on such small numbers
The statistic measures what the statistic measures. If you understand that, there's no problem. Of course you shouldn't look at it and conclude "Taiwan rules" and "China sucks". Because yes, the numbers are small and there are biases which would need to be taken into account to draw conclusions. But look at it this way: the data can be used to find these biases. Consider the bias an observation in itself, rather than a hindrance for observations. Instead of concluding
"Indians suck at cubing" you can take their low value as indication that
"Relatively few Indians have participated in WCA competitions", and then you can ask why that is and so on.
The statistic itself is perfectly fine. Problems only may arise once people draw conclusions from it.