The way the zombies are spawning now is how it was always supposed to be. A few months back it was brought up in the Support section of the forum that zombie spawning seemed too low or even nonexistent, especially in the pine forest, after a few days into a game. Jugginator looked into it and confirmed that something was wrong. It was something along the lines of if zombies weren't killed but timed out (died on their own) then they would never respawn again. The more zombies that timed out, the less zombies you'd see as the game progresses.
The initial fix did affect non-zombie animals meaning they were spawning way too much. That has since been fixed.
It could be that feral sense might need to be tweaked now that the spawning is fixed. Without feral sense on, the zombie spawn rate seems appropriately dangerous for being in a city of a higher gamestage biome.