I think it's a matter of you finding the happy medium between resolution and fps, you could also try lowering the resolution of the input images maybe.
I'm surprised to hear qtz is running it smoothly.
Fire periodically is what I had expected to work.
I have noticed a big drop in performance with multi-pass shaders...reducing to really low res, sometimes lower than 1280x720 and 25fps to make some function smoothly on my crappy mbp.
I think the jerky frame rate would be solved if you fed the composition a constant time/frame rate.
When I run the shadertoys I've copied into Freeframes for Resolume they play jerkily until I cap the frame rate.