. So... It's like assuming Shadowheart killed FOUR devourers herself just because the bodies are near her, or assuming Gale singlehandedly killed the goblin patrol because their bodies are near where you meet him. You have no real reason to assume that's the case. You just assume because you have no other real evidence.
Well,
actually... I noticed that in patch 8, if you don't let Shadowheart out of the tank, you can meet her at the chapel door instead of lying on the beach. Then, if you tell her that the noise she's making might draw enemies... Shadowheart comments smth like 'who do you think killed them' or 'those didn't die by themselves'.
On the other hand... and I might be a bit cynical... Gale is callous, demeaning, and threatening when you get him angry so if he thought he didn't have anything to gain from rescuing you, he'd likely have left you to die on the ship. Just like you can leave Shadowheart... and just like Astarion complains that while he was trapped, you were just 'strutting about'. Just selfish bastards all around (Tav sometimes included)
