I checked snopes.com and they’ve thoroughly disproved this...
I was the one who posted a couple weeks ago. The only thing using full lineups does is use more heroes to dominate already weak heroes.
We had a couple cyan lines mixed into our crypt today for the first time in 5+ days. We’ve had no more success with our crypt than before and we’re probably going on a good month of trying.
If I had to guess, I think it’s based inversely off of team level. It seems as we grow higher and higher, the weaker crypt gets. My gut feeling is that there is some variable set to hold 128 values (e.g. 0 to 127) that is used in the calc. As we exceed it, it’s flipping to give us the purple and orange lines (e.g. generated for player levels of 1 to 38).