Your looking at CPU ratio, i'm guessing pCPU:vCPU?
Cloud providers tend to run 1:20. So if you work for a cloud provider you're all good! All kidding aside it depend on your workload. I've seen end users face issues with a ratio of 1:2 while the cluster hosts large and heavy IO database VMs. But if you run simple web servers that number can go up much higher. The higher the ratio the higher the chance that end users will face contention.
Check the "what-if analysis" if you can add extra hardware. Or you could check CPU reservations or maybe migrate VMs to another cluster.