Rudeus actually did foresaw his own gruesome wounding, and was able to avoid the first hit, although Ruijerd actually made most of the evasion happen. However, Rudeus doesn't, very evidently, have the mindset of a fighter, despite the long journey through the demon continent. That's why I said he's not only benefitting from his past life on Earth, but it's also a big weakness. He can't, by default, process a situation where another humanoid he can even talk with would be totally unreasonable and hostile. It's actually kind of funny because back on Earth he was mercilessly bullied, which is unreasonable hostility. But he's still a Japanese pacifist deep down. He simply didn't have the tools to face Orsted in any manner. We can assume Orsted is beyond powerful and experienced, besting Ruijerd handily, so if he intended to give Rudeus a fatal wound, it would be a fatal wound.

Orsted is not a third party, he's the second party. Like I said, his reason for killing Rudeus is quite flimsy, so why would he need an especially heavy reason to heal him either? If he's a so called god, it must not be an especially big deal for him.