I was making an overcast diffuse lighting with area Lamp Size 10. As you can see on top right there are cubic shadow. I am rendering with 1000 samples 4k Shadow and above that nothing special happens except render time becomes longer.
Although I can make lamp size smaller to reduce the blocky shadows, this will make lighting not diffuse enough to become overcast weather.
Both at 128 samples and default shadow map resolution. There’s a big difference in light fall off, but the quality is still way better even when using a small amount of area lights than a single big one, where the fall off is more similar. You could also try irradiance volumes, but I’m not a big fan of how fiddly that whole workflow is.
In general I’d try to solve this with multiple lights with different settings. Or if the time to light it takes too long then switch to Cycles.
Edit:
After some tweaking, raised the samples and added sun lights with slight angle varitations to combat the light fall off of area lights:
Could definitely be arrenged better. Also contact shadows don’t work that great in this case and some of the odd shadows on my last render are due to that. Disabling them on light arrays fixes that.