The spawn rates definitely seem higher. They will probably be getting a tweak soon.
I have a hypothesis that the chance to spawn is probably similar to what we have always had. Just that there are more things able to be spawned now and it is treating spawning as separate events for each enemy type, rather than determining whether or not somthing spawns and then what spawns. So like say (these numbers are completely made up) skeletons have a 10% chance to spawn, ocean crawlers a 10% chance to spawn, and phantoms a 10% chance to spawn. So basically rolling a 10 sided die and if it's a 1 somthing spawns. The game is probably "rolling" for each of these events separately, so essentially rolling more dice than it used to. Since the spawning events can only happen for a limited ammount of time, a player being on an island (or in the water in the case of sirens and sharks) it seems like the overall spawn rate is increased. You are more likely to roll a higher ammount of 1s in a minute if you roll 3 dice a second than 1 die a second. There may also be some sort of queue system for triggered events that leads to it feeling like waves of enemies spawning.
But that is all wild speculation and not backed up by any evidence. Just a hypothetical explanation for the seeming increase in the global spawn rate. 🤷♂️
