The game's framerate is 30 FPS. Every step is therefore 1/30 of a second. There are some checks every step: Your health cannot exceed your maximum (exceptions: 1 step) Your mana cannot exceed your maximum (exceptions: 1 step)
and much more.
This includes Zombies, a few beasts and Azukyri. The slowest ticks are 9/30 of a second (yes, enemies can attack you that fast) These zombies do high damage Zombie's ticks are 8/30 of a second. Azukyri's tick is 7/30 of a second. This damage tick is unique.
Skeletons can attack you every 6/30 of a second. This does not mean they are overpowered, but rather do medium damage. Most beasts can attack you every 5/30 if not 4/30 of a second.
Here are Betrayers. They can attack you at a rate of 1-3/30 of a second. They do extremely low damage, but their damage per second is only topped by Azukyri.