Some research in America on post hooking survival rates in Northern Pike showed that they seem to survive catch and release rather well. The thing that was most likely to result in death was deep hooking, way in front of bad handling or even time out of water. They found that one of the biggest killers was small trebles as they had a tendency to be swallowed further. Large trebles were found to be better for the pike and lure fishing was best of all as the pike didn't get chance to swallow the bait.
years ago i watched Andy Macfarlane dealing with a pike he had caught fair and square in the mouth. he discovered someone elses deep hooked deadbait trace. couldnt tell how long it had been deep hooked for but it could have been a long time, weeks perhaps?. it obviously survived the initial deep hooking and felt the need to eat as it took Andys bait.
deep hook was dealt with and the fish swam off. so again i dont think anyone can really say 1 way or the other if a fish is destined to die so i think its fair to say nobody here is right or wrong.
thats not to say i wouldnt consider putting a fish out of its misery if i were so concerned.