I can see two possible reasons for the flickering in this animation:
1) Not enough AA - in this case the solution would be to just allow more passes to be rendered, either by spending more time per frame, or by lowering GIvsAA balance, to have more passes rendered in the same time.
2) Not enough GI samples (responsible also for glossy reflections) - in this case the solution would be to either allow more passes, or to increase GIvsAA balance, to have better quality of reflections.
I would do a region rendering, and try both methods to see which one helps. Most probably more passes per frame will be needed anyway.
Using highlight clamping is an option too, but remember that it will kill the dynamic range in your image, so you won't be able to take advantage of 32-bit formats if you need them. I would start with some low value like 1 and see if there are no artifacts like dark highlights, and if there are, increase it to 2, and so on.
Using bloom and glare + sharpen/blur is also a way to deal with strong highlights.
