Those above level 6 wont have access to CC. So there are only maximum 3 diverse battlefield that anyone of any level can participate in.
Then why did Cross Knight say "you have to take part in all at least one of each of the FOUR battlefields" ... wouldn't that be THREE then?
And btw one more thing as the original answer isn't 100% clear: does someone who participates in all 4 once have the same chance as someone who participates to all 4 but more time in each?