I will point out that borgmon's language (minus macros) is almost a 1:1 match with Prometheus. You can judge for yourself how crazy that is, but I feel that it's close to as simple as you can get for the power it gives you.

As for Monarch, it's a very different beast. For one, it stores all its rules in a protocol buffer format, so it's more structured. But then you have to write Python code that generates the protocol buffers and pushes them to storage. It looks similar but not the same as the ad-hoc query language. I wouldn't go as far as calling it sane.

It is also a service and it's optimized for Google's network architecture with datacenter local and global nodes and the language itself is aware of this distinction and some computations are done locally, others globally and so on.

For your local monitoring needs (or even global ones, if you're willing to put in the effort), Prometheus is a solid choice.