I chose eth1 for Mirror Server IP on both machines, is that what you mean with dedicated Volume Replication NIC?
Yes the volume groups are both named vg01.
There are no VLANs.
Yes, as I described in my initial post, they can both ping each other on all IPs given.
The NICs actually have no working gateway anymore, because that would be 192.168.3.1 and I wanted to keep them in a different subnet because of the vIP (192.168.3.210) which should be accessible by the other host in the network.