That is wild and definitely not in line with the behavior we saw when a motherboard failed
in one of our small 3-node oVirt 4.5 clusters. The bad host hard-froze, shortly after that
one of the surviving nodes fenced it via IPMI, and all the VMs that had been running on it
were started on surviving hosts.
It sounds like your experience is that a single node fails (even one with no VMs on it at
the time), and the surviving hosts shut down (or do they kill) the VMs that they have
running. Is that accurate?