I do have ready access to any casualty studies from the Wars of Succession. However, one study of Waterloo [granted out of ETW's time frame, but my limited knowledge of medical military history suggests there were not significant advances between 1700-1815] done in the 1970s, suggests that the death rate of wounded in British field hospitals in the immediate aftermath of the battle was about 9%. Given that about 55% of the total casualties suffered made it to a hospital, that means about 45% of the total casualties survived the fight.
Shelby Foote in his history of the American Civil War, used the rule of thumb that 50% of wounded return to their army eventually when doing a casuatly analysis of the Seven Days. Aknowledging that the ACW was a different era, we can for the sake of this argument assume that things were alot worse in the 1700s, and that only 25% of wounded returned to their units. That would still mean, that on average, about 11% of all casualties should be recovered after every fight.