Yeah, it's the same core issue as the rotation problem--the new hardware is more sensitive to cache misses, and these algorithms are a worst case scenario there. I reworked the blur function, grouping the data so that it fits in data cache better, and got it up from 20% of the rev A speed to 75%. The casual birder demo case above runs around 16 fps now.. Not ideal but a lot better than before.
I'll try and get the fix on the schedule soon! It won't make it into 2.1, but hopefully 2.1.1. Thank you @adamblance for the excellent bug report!