While i have to agree that there are performance issues, there is something you can try as a temporary fix.
Check this page out: http://opendayz.net/threads/dayz-performance-increase.17704/
At the time of writing, the forums seem to be down for maintenance, but i've added a link to a cached version;
What was the condition of the cuffs?
The worse condition, the higher chance of breaking free.
Regarding you seeing him still being cuffed - this has something to do with the netcode and possibly your routing to the server you were on.
Sorry for duplicating. Didn't find the function to search through issues.
A screenshot would be helpful here.
As of revision 0.30.113860, you will now die when leaving the server in unconscious state.
"Design: players who disconnect when unconscious will die"