Yes, too many accidents in US EMS. Would somebody please post a US EMS accident rate? I suspect there is no sound statistical means to assess our accident rate, and I'm convinced that were there such it would be heavy on pilot error.
It's not a single/twin issue, you don't have to go very far into the history to see twins involved.
It's not a VFR/IFR issue, see previous.
It is a day/night issue- NVGs and scheduling.
It's a training issue, night training especially.
It's a managerial issue: all give safety lip-service, but often fail when the almighty dollar becomes an issue.
It's a regulatory issue. EMS is not just 'unscheduled fly-for-hire', and that is obvious to everybody flying the line. There are industry specific Parts for Ag and External work- EMS needs one too.
Finally- I'm coming around to the conviction that this is a single-pilot issue above all else. Pilots who can do this well by themselves are a minority and the safety advantages of a 2-pilot crew are inarguable.