I'm playing next to Prime Minister Esirce, and his spawn rate for great people and adventures seems out of whack. It's turn 250 and he has 12 hero's and he just spawned two bards on the same turn. Both of the bards came from cities and not dungeons. It seems like every city acts as it's own civilization. I dont notice this when playing any other leader for grigori.
Getting two Bards on one turn is possible, but rare. I've done it when my city produced a Great Bard 'regularly' and I was the first to research Drama.
However, I agree with you that in my FF games (seems like eons ago since I played though as I upgraded to 3.19) the Grigori were popping plenty of Adventurers and GPs. I know V fiddled with the spawn rate of the Adventurers, however, I think it was still borderline in favor of the Grigori getting one every 25-30 turns on average.