Wow. She's pulling all the tropes so tsun that it almost feels like a parody. I guess it's just been a while since I saw a full tsundere.
I don't think their decision was wrong there. You can't depend on Garius for everything, so they brought someone with sharp senses and someone with high magic skill along. They probably could've fought the humans off to an extent since they only needed to cover 2 people's escape, but this makes sense too since they know the humans want to capture them, which makes a decoy and rescue always an option.
You know, something had occurred to me while I was rereading this. Could Garius's figure despite being a Hero be because he's inadvertently "fully using" any food he consumes?