I'd like to disagree. This is not a vCenter issue but a host issue known as APD/PDL. The delete without the detach is what is essentially killing hostd on all of yours hosts and with 5.0 there is usually no clean way to come back from that kind of situation without a reboot.
More information can be found in the following 2 kb articles.
VMware KB: ESXi/ESX hosts in APD may appear Not Responding in vCenter Server
VMware KB: Permanent Device Loss (PDL) and All-Paths-Down (APD) in vSphere 5.0
Also make sure that everyone follows the exact procedure to remove LUNs from the hosts before deleting them (you seem to know but that doesn't help much if someone else is not aware of it).