The following document discusses ISE performance and scale in general, including TACACS+; however, it assumes a dedicated PSN for TACACS+.
https://community.cisco.com/t5/security-documents/ise-performance-amp-scale/ta-p/3642148#toc-hId-1865558232
Many customers do not want to combine their Device Administration ISE deployment with their Secure Access/802.1x ISE deployment. There are different reasons for that and is outside the scope of this discussion. With that said, many customers will deploy their TACACS+ ISE deployment as a standalone pair. Can we get performance and scale numbers for a standalone deployment?
