If all the following hold
- More than one CPUs in the VM
- Pinned your VM (via your host) to specific dedicated CPUs with a 1-1 mapping
- The VM has dedicated (e.g. via passthrough) access to storage/network hardware
then in-VM IRQ rebalancing still makes sense.
Without multiple CPUs in the VM, in-VM IRQ rebalancing obviously serves no purpose. For the other points things become tricky because the "real" CPUs your VM is sitting on could be shuffling around underneath you and you don't know which of your virtual interrupts are going to be handled by which real CPUs. Additionally, if the real CPU is being shared between multiple VMs you don't actually know what other work it is doing or when it is going to get around to servicing things so the "virtual rebalancing" could actually be making things worse...
PS: It will just be /proc/interrupts that you will need to look at.
PPS: Two years ago isn't that old! Some information is timeless...
PPPS: VMCI is vestigial and isn't supported on ESXi 6 or later.