What you were expecting to happen, and what actually happened:
Heroism scrolls were supposed to be distributed more evenly within Tower of Doom, granting all guilds roughly the same amount for the same number of tower levels climbed. This seemed to have been implemented with the Tower of Doom run five weeks ago, Heroism scrolls showed up quite regularly. The current Tower of Doom appears to have returned to the “pray to get lucky” handling, we only found a single Heroism scroll on the first 25 levels.
Lacking further insight my assumption is the the improved handling didn’t get added to the 4.3.5 update, causing Tower of Doom to revert to the old, entirely random Heroism distribution.
I don’t think the would tell us, they are usually either not aware of changes to game mechanics or not willing to disclose them. There was definitely a new scroll distribution pattern active the last Tower of Doom run, the overall layout was so much different from previous runs it couldn’t possibly have been a random deviation. There’s a somewhat reasonable chance we just got unlucky on this run, which further data will tell. It feels much more likely this is yet another code regression though, those have been happening a lot lately.
I can definitely say that I’ve noticed a huge drop in Heroism scrolls as well, only 3 up to floor 50 compared to over twice as much last time at this point. Same thing goes for other guilds in our family, so it’s starting to look less and less like a random unlucky streak.