I have done an IT dedicated VMWare cluster with these machines:

1: One's log manager of choice, be it Splunk, elk stack, or whatnot. 2: An instance of some Git server (GitLab, BitBucket, GHE) for stashing documentation and disaster recovery stuff. The Git server also helps with masterless Puppet installs (puppet-apply), Ansible playbooks, and so on. This is an IT-only Git server, and has nothing to do with development, but more for notes and how one gets a machine up. It essentially does the duty of a wiki, but with the laziness of just writing Markdown text and committing it.

This instance also stores copies of license keys and such, so finding that master key to enable a NetBackup media server isn't an exercise in frustration.

3: A VM for enterprise password management. Runs in FT mode, since it is relatively small, and needs to be up. This replaces the "sealed envelope with the root password", as every machine should have a different root password these days, be it Windows boxes and local admin or UNIX boxes and root (assuming root isn't a role like Solaris 11.) 4: A private build server. Something where one can build custom code on can use. 5: A Splunk license master. Definitely FT mode as well, due to size, and how often slaves phone home. 6: A mirror of major Linux distributions and fixes. Yes, a cache via Squid or varnish is better, but in some environments not connected to the Internet, having a server which fetches updates, validates their signatures (dumping any whose siggies don't jive), and having it available for internal consumption is the only way to do it. This also stores admins' SSH keys, so on provisioning, it is easy for a script or a manifest to fetch a copy of the latest authorized_keys, and drop it into root's .ssh directory. 7: A syslog dump. Syslogs are tossed onto the machine, shoved into Splunk, then archived or tossed come logrotation time.

tl;dr, I wouldn't say one box is useful, but having a dedicated cluster can make IT life easier, and help with institutional memory.