I wonder if some nodes start out "cooler" than others, that is to say with lower odds initially.
Some nodes, like the veteran Han/Chewie, seemingly go through long dry spells before catching up. Others like the KRU/Silencer node go through shorter spells. It may be observer bias since everyone wants KRU and he is on a low energy node so dry spells are shaken off and the vets have very little use outside of getting JTR and are on a high energy node so dry spells are more painful.
Ultimately that 30% shard rate seems consistent so it all averages out.