I haven’t tested hard CPU quotas with Nomad but I suspect the issue mentioned above is due to cgroups/CFS and is also applicable to Kubernetes. See these slides for more details: https://www.slideshare.net/mobile/try_except_/optimizing-kub...
I had the exact same problem with Kubernetes (and even just straight up containers), I just want to make sure folks are extremely aware of how big of a footgun it is, and to really, really, really test it well.