The article listed states 276 related reports of death after taser use since 2000. I'd imagine tasers are used a few hundred times per day across the US, if not more.
Yeah your number's surprisingly (to me) actually not far off.
Use of Tasers varies pretty widely from department to department -- according to [1] the Richmond County SD reports about 0.053 uses per officer-month, Miami-Dade PD about 0.0074 uses per officer-month, and Seattle PD about 0.056 uses per officer-month.
Extrapolating the RCSD value across the US, with over 800k officers total [2], it comes out to about 43k uses per month. Given the ~200 months over which this data was gathered, that's 9.2M uses, which makes the 276 fatalities only 0.003% of all incidents (as a best-guess).
Obviously that in no way implies Taser's behavior was ethical; but it's actually a surprisingly low fatality rate for a weapon still considered somewhat lethal.
This is simply not true and weakens your argument quite a bit.