Add an option to only show cooldowns on boss encounters.
Also I notice that the addon for my shaman isn't recommending the use of Earth Elemental in any circumstances, I wonder why.

Just toggle cooldowns on/off before/during/after boss encounters.

Earth Elemental isn't recommended because the criteria for it are literally "just use it on CD if it's not going to overwrite a real DPS elemental." It is far better to save it for utility.

But you can add it into your own custom priority if you desire.