1. It's an emergency, and said untested had just provided a plan that could theoretically make safeguarding sword bearers ridiculously easy.
2. Said untested also has a prior record of achievements that has been verified by several other members of the organization
3. Teleport guy did not go to the headquarters with them due to a poor relationship between him and the organization.
4. That said, Teleport guy is likely already there considering the distance to the site would need him to help out anyway, especially as this is an emergency.
Tldr, read the chapter, then wait for the next chapter. It's not like the author has given a reason to doubt his story beats so far. Even if not original, it's very solid and is supported by the author actually being able to tell a story well.
1. Utter nonsense. But at least you divided it into 4 neat (and useless) nonsense points, so I'll return the favour.
2. All of the top brass there are top level fighters, if losing a sword bearer is so critical, they should have gone to protect him. No one is saying they can't also send MC. There is absolutely no need to spare resources on this and this is not a situation that's fitting to test a new guy on. Their fortress was annihilated, they should know this is not going to be easy.
3. MC and storage boy just got back from a tough fight, and storage boy can't even use his magic. Which almost resulted in the sword bearer dying. They were an inch from disaster when they had no reason to be.
4. What does it matter where teleport guy did or did not go? He can teleport...
tl;dr This is bad story-writing, prioritising plot convenience and cool scenes over common sense. You can like a manga and still call it out for BS when needed. Or you can be weird and be personally offended by someone's opinion on a manga chapter like you drew the damn thing.