@thenajsays said:

have light as an emissive material currently, but I've experimented with various setting, IES lights and spot lights, and I still see the same issue.

Did you try rendering the scene with no emmissive material? Try to get your lighting right without the emm. mats to make sure you have enough light in your scene.

@panixia
Increasing the HSph. subdivs in the irradiance map settings will help reduce the splotchiness, but it won't fix the emissive "sparkles" that we see.