The biggest issue with control panels is that most (the majority) are not built for cluster setups. Using cPanel as an example, last I recall, you can offload MySQL and DNS, though the DNS offload is very basic and offloading MySQL limits your support through their channels as MySQL is intended to run on the same server cPanel is installed on.
Offloading MySQL with cPanel is also just that, offloading MySQL. It’s not a master-slave configuration, nor are there options to set that up (you’d still be stuck using the CLI). Even if you did set it up, if you ran in to issues, cPanel most likely wouldn’t provide support since you are breaking in to the custom configuration setup and need to know what you’re doing and how to handle it.
cPanel, Plesk, VestaCP and many others will allow you to easily manage same-server configurations, but when you venture in to multi-server clusters, failover, load-balancing, etc – you’re really venturing in to an area where control panels fall short.
Last I saw, Plesk does allow you to manage multiple servers through a single interface, but each of those servers, in turn, also needs to have Plesk installed and then you’re stuck configuring each one to remove Apache, MySQL, etc when they aren’t needed so they don’t needlessly consume resources that are better used elsewhere (i.e. Memcached, Varnish, Redis, etc). Once you do that, you’re pretty much left with a control panel that doesn’t do very much.