My favorite quote "there are 3 types of lies... lies , damn lies, and statistics". THW has 13,490 matches recorded from over 69 events since drop of GHB 2019.
In my line of work we use data sets to actuality make decisions and decide courses of action. What you propose is more of what we refer to as analysis paralysis. wanting a 100% perfect set of data before you can draw any conclusions is impossible in reality as you can never get it from something like this. If it is 80% direction-ally correct you can draw conclusions from the data.
Take storm cast vs skaven
Skaven make up 8.33% of the sample group with a win % of 55.6%
SCE are 9.21% with a win rate of 43%.
We know Skaven have become much more competitive since the drop of their new tome. The data reflects that and the SCE under preform in comparison . sure there is going to be some noise in there but data always has it.
can do same comparison to Night haunts vs DOK. AoS is not well balanced for competitive play and the data shows it.
Source data
https://thehonestwargamer.com/13th-december-stats/