Have tested this node in one of my tesscenes (a Paper2D world with Jump&run stuff), and that alone dropped the usage from 43% to 7-9% at max, while the HUD was still rendered and functional. Which makes that node really interesting for pure 2D games ^.^
However, my game has vsync enabled, or smooth framerate, because without it, i ran into the issue, that it was capped to 120 fps in editor, but in a testbuild, it ran on unlimited power, making the GPU run like crazy at 99% usage.
And maybe this video helps you, maybe something else is off:
