Next week they are planning on adding additional load to one of the VMs and were wondering if perhaps VMware might have automatically tuned the host based on the load it had experienced so that when additional load is added, it would not perform that well.
Não foi. Essa funcionalidade não existe.
Are there any steps I need to take to make sure it performs well with the added load?
Sim, verifique se você tem os recursos disponíveis para lidar com a carga adicional. Assim como qualquer outra coisa.