but i would suggest to take a closer look at the Random Number Generator that STO uses too.
"Random" or "Shuffle" are often just not random enough.
Take a Winamp list of 5000 Songs, always listen to that same playlist in Shuffle mode, after a few weeks/months you will notice that you hear the same few songs over and over again, even in the same order, and notice that other stuff is never played at all.
-> my money is on the RANDOMIZER to be just not *random* enough.
Probably the same reason the DOff Upgrinder spits out more Purple Bartenders, Chefs and Sci Officers (for 5000 dil a pop) than anything.