I too am experience a slowdown from 30 FPS on Blender 2.79 to 10 FPS on Blender 2.81, on the very same characters from Resilience Satelle.
I’m at this moment convinced that this is not an issue of the graphics card (I have the NVIDIA Titan X) but of the CPU (I have a 5 years old AMD A-10). Anyone has a recent CPU (powerful CPU 
) that can make a test on this.
That is probably why we can rotate the viewport fast, because it’s using the GPU to do that, and playback of the animation is slow, because it uses the CPU and for some reason it got a lot more heavy on 2.8 