Another open source tool that does something similar is https://k6.io/ which I have been using recently. Tests are written in JS and you can define thresholds such as % errors, P95 and P99 response time for specific request components e.g. blocking, receiving, waiting, etc. There is also a SaaS product connected to it for doing tests from locations around the world.
I'm one of the people behind k6 - thanks for mentioning it :)
As for Locust, I've been testing and reviewing a whole slew of load testing tools, and blogging about them, and Locust is definitely a favourite of mine. It used to perform badly a couple of years ago, but with the new FastHTTPLocust class its performance is quite OK and it's the only tool that allows you to write test code in regular Python (there is another tool - the Grinder - that also lets you write in Python, but it is Java-Jython which means no pypi libraries). If you're into Python you should definitely try out Locust.
