The pacing was fine due to the anime being a prequel to what happens in the magical world. I know prequel isn't a good word for it, but the reason so many characters are killed off is because it isn't meant to stay on Earth. Pretty much, it leaves off as the MC finds out it's all bullshit. I need to read the LN all the way through so, I need to know what happens, I also think that it deserved a second season, but as with most good animes, it doesn't usually happen.
Definitely watch it tho, I enjoyed it, and it was way better than Madoka, even though it's fairly different, like you said, a battle royale rather than a team of magical girls saving the world.
