Changing spawns to make them like the real game (help)

Im doing a new Pixelmon server again. The last one i did was super fun BUT, myself and others really hated the legendary farming aspect. It was just dumb to us because to get legendaries you would just afk in areas or teleport to waypoints when the legendary spawn chance was about to happen. Is there any way to make it so legendaries spawn more naturally? The only way i could think was to make them spawn every 10 seconds or something but with an insanely low chance of spawning. Even though it doesnt solve the issue fully, atleast then you can technically have a chance at finding them constantly. Is there any other way to do it? If not, does anyone have any suggestions on the number i should use for the method i mentioned. i.e. The spawn chance and the spawn intervals.