Yeah, probably not enough spread etc with the barbs and no follow up to the calf muscles. If applied properly there is not much a person can do to fight through it due to it all being involuntary.
Months old post I know, but you'd be surprised by some of these psych patients. Every patient is of course different but the violent ones are often juiced up on a menagerie of pharmaceuticals that effect/impair neural function. And the bigger ones are harder to dose, so they end up getting far bigger dosages, especially on a day where they're having an episode. Usually by the time the cops arrive to the psych ward it's already been escalating for some time, plenty of adrenaline, blood pressure through the roof, etc. Plus in general many of the severely mentally infirmed have a big assortment of other health issues which aggravate their condition, and also adds a whole extra cocktail of drugs to the mix. Even seemingly common things like diabetes impair your nervous system. And then some crazy people are literally crazy because their neural pathways do not function the same way yours or mine do. So altogether, it's very well possible that a patient might not even feel that he's been tased, but still be able to stand, throw punches, etc.