A swamp cooler is basically self-regulating as to the amount of moisture it injects into the condition space.
When you have 80% relative humidity in the morning the amount of moisture added by the swamp cooler is negligible. As the heat of the day arrives and the relative humidity falls, more moisture evaporates at the swamp cooler (subsequently lowing the air temperature).
Again, 70°F 80% relative humidity is comfortable. 95°F 36% relative humidity is not (and they contain the same volume of water vapor). The reason is a sensible rise in temperature, not the percentage of relative humidity. Adding humidity resulting in lowering or keeping the temperature at 70°F does not make you uncomfortable because of the increase in percentage relative humidity.
Two of the comfort factors that come to play here are temperature and humidity.
When the temperature gets up to or above your body temperature you begin to feel hot.
Higher temperature migrates towards lower temperature. The lower the rate of heat transfer the warmer you feel.
Based upon the amount of perspiration you are generating (proportional to your activity rate) relative humidity affects evaporation rates off of your skin.
If you are not perspiring, the relative humidity of the air has less effect on your comfort. If you’re highly active and perspiring, the relative humidity of the air is significant because you become the swamp cooler.
If you are sweating a lot, relative humidity is a greater factor. If you’re sitting behind a desk, dry bulb temperature is a greater factor.
Do not think of a swamp cooler as a humidifier. A humidifier uses heat to change the state of water to a vapor. A swamp cooler does not. The rate of evaporation is based on the relative humidity of the air passing through the machine. Heat of the air is used to change the state of water to vapor. Vapor still contains the same quantity of heat energy but the sensible heat you feel is lower.
From a different perspective; being a warehouse you probably have a lot of air changes going on. If you lower the temperature within the building from 95°F 36% relative humidity down to 70°F, you are creating the muggy atmosphere because you lowered the temperature without removing humidity. It’s not because the swamp cooler is adding to the percent relative humidity, it’s because a swamp cooler does not operate below the dewpoint temperature and cannot remove the latent heat which subsequently lowers the sensible heat like a refrigerated air conditioner does.
Because you have a warehouse in this situation and subsequently a large air exchange rate, there is likely to be a point where you will exceed the capabilities and therefore move outside of the comfort zone utilizing an evaporative cooler. We need the specifics to make that determination.