NC's lack of taser-related policy is alarming (and not likely limited to NC). Many counties have nothing in place and allow tasing of already-restrained suspects, the elderly, and pregnant women. The report is worth a read; data regarding tasers are difficult to come by.
Sadly, in the end, the NC Taser Safety Project was left to approach law enforcement agencies with their data and accept whatever responses the agencies offered. They were effectively turned away by the North Carolina Sheriff's Association.
It's clear from ever increasing taser use that the police are not going to autonomously develop acceptable policies for tasers. Change will require formal, transparent, community involved, and authoritative oversight. Expect more of the same until such oversight happens.
One other note of curiosity, the report doesn't examine racial and economic factors in taser use.