My attempts in realizing the setup in the question didnt produce any results over 3 full days' of research and trying. The HA services necessary are Apache which serves numerous virtual hosts each from its own user account, MySQL which serves in the same fashion, and any files which may be uploaded from Apache to these user account's web roots.
I have 2 dedicated servers, one Failover IP which can be used through a web api to point to either server, 2 additional dedicated IPs for 2 servers. I am not able to use Multicast.
I tried with many different stacks, ranging from RedHat's own Cluster packages to various Pacemaker setups, in the closest attempt I was able to have Pacemaker see both nodes as online, whereas in each machine cman wasn't able to see the other node.
Is it possible to set up a CentOS HA cluster with the resources mentioned?