I wouldn't say that... if they wanted us dead, there are more efficient ways to do so. They do have a habit of unleashing dangerous animals on us — it wasn't that long ago that we had raptors running wild and before that, there were swarms of giant hallucinogenic hyenawasps.
I'm not implying that they're doing it on purpose but I'm also not ready to commit to the idea that they're just incompetent. This could after all be a giant social experiment and watching us cope with unusual or surreal experiences would be... intriguing.
At least, that's what I would think if I was a Warden.