Chart of intra-species genetic diversity across species / phyla?
You can look at the Heterozygous SNP rates in genome-sequenced species, which is a measure of within species diversity.

You have an example in Figure 4 here:
https://genomebiology.biomedcentral.com/track/pdf/10.1186/s13059-016-1090-1

You can see in the figure that endangered species are plotted (most of them with poor genetic diversity).

Also, I am afraid that your starting hypothesis is not very good. Our species is very poor in genetic diversity and has little phenotypic variation. The human species went through several major bottlenecks during his evolutionary history that reduced their diversity. Even gorillas or giant pandas are more diverse than humans. You have a bias because you are human and are good at differentiating individuals from your own species.

Also a single representative from each group won't suffice as the differences can be huge inside a group. Additionally phenotypic variation is hard to measure in certain groups.

Sorry for being a bit negative