I just had a look at Magneson's SVG to XML approach, it's a bust for me (or would take a lot more work and I can't imagine it amounting to anything except an experiment). SVG's parameters for paths include move (M) and curve (C -- provides 6 parameters per point for cubic bezier curve).
We're seeing similar results with a 1920x1080 Hap1 video (Gadane Fega Hap HD.mov from Hap Sample Pack One 1080p), tested on one computer. Vuo 1.2.8 is using a lot more CPU than VLC (Vuo = 101% – 125%; VLC = 25% – 58%).
As it turns out, Hap has two APIs: a simpler one that Vuo was using and a more complicated one that is apparently the fast one. With the fast API, the same video uses much less CPU (12% – 19%). We'll switch over to the fast API for the next release.