I'd say it's down to personality of the puffer. I've got 3 dwarfs happily living with an amano shrimp, but this might just be fine as he's so much bigger than they are, but they've not been tempted to have a nibble on his legs or feelers yet. I have avoided feeding the puffers any brine shrimp though just incase they get a taste of shrimp and want some of the amano!
If they dwarf is introduced when the shrimp is already there you may be alright, put the dwarf will very soon learn that nearly everything that's put in the top of the tank will be for it to feed on.