I personally feel faster blinkers get more attention up to a point... Its a feature not a bug.
Too fast is just as detrimental. That's why the CUSTOMLED unit rocks so much! you can change the strobe rate to solid any where from 0 flashes to 7 flashes before becoming solid. I've found that 3 flashes before solid seems to be the most effective in getting people's attention.
i dont think faster signal is going to cause target fixation thats kind of silly and there is no right speed. faster gets more attention and guven that cagers are or can be blind to bikes themselves ( the entire bike and you on it ) more attention cant hurt