I noticed this as of 1.11.1. Was dealing with the disaster of new villagers and mechanics when 1.11.0 came out to come to guardian farm. But since i have decided to abandon villager trading and start using dupping until you can fix villagers. I am now free to play the game again instead of trying to play glitchcraft with the villagers.

It seems like guardians spawn for a bit then stop. And will not start again unless you go peaceful and then go back into hard mode. Have done 3 peaceful purges so far. Last ones were done while eating so unsure how long to stop spawning or if based on number of spawned. Just now seems like they stopped after 5 to 7 min. Playing on realm.

Ok just now went from hard to normal to easy back to hard. And no spawning. But did a peaceful purge and within 30 to 45 sec started spawning again. 

Before update had history of none spawning outside of farm. I have several times checked the perimiter and as much of the water caves i can. Can find no guardians in the area. Have 3 conduits surrounding the farm to swin. And huge area of bubble columns next to farm. Left over from failed attempt at first farm. 

I have a feeling this is related to the recent guardian bug fix for spawning on dry blocks. 

I have to be honest this is not a game breaking bug for me. Would rather see villager issue fixed asap or reverted to old villager system before this.