I've never cared enough to look up the details, but it seems that every pokemon put in a gym will decay to some minimum level (which appears in red numbers when reached). If the real world time it takes each pokemon to decay to this minimum level was the same for two pokemon put in a gym at the same time, it would make sense for the one with the higher CP to decay at a faster rate as you described.
GamePress
Gym motivation decay explanation please
Looking for some smart people to explain gym decay for me. I have two Pokémon in gyms that are ~2600 +/- 70 CP. After 3 hours from full motivation (raz, 1+ days defending, 3 other defenders), the lower CP one has lost 850 CP (~280/hr). After 2 hours, the higher CP one (regular berry to fill up new defender, 1 other defender) has lost 350 CP (~175/hr). Are there other factors (time in gym, total gym motivation, weather, type of Pokémon, etc...) that also impact motivation decay?
I had thought it was pretty straightforward that decay was solely dependent on starting CP. The faster decay is on an EX gym? Do they decay faster?
Interested in all explanations.
