Judging from http://joeyh.name/blog/entry/7drl_2015_day_2_level_generation_and_game_concept/ I wonder if the "so few calls to the RNG" is all that unusual in modern roguelikes.  It is my understanding that most procedural generation systems in use today go with a single random input to a collection of noise functions (perlin, etc) to produce the emergent complexity. 

Part of the reason for this is that you can plug an integer into the game at the start and get a repeatable debuggable testable scenario.  Brogue even has "seed of the day" challenges where people rush to see who gets the best score for a given initial seed within a 24 hour period.

I think three calls to the RNG per level is unusually high, for 2015!