The current setup seems to be working and is this...
Port 1 - Solaris 11.1 - ConnectX-2 (SAN)
Port 2 - ESXi 5.1: ConnectX A2 (unflashed)
Port 3 - ESXi 5.1: none
Port 4 - CentOS 6.4 (OpenSM): ConnectX A1 (flashed)
Port 5 - ESXi 5.1: ConnectX A2 (unflashed)
So, the two core ESXi 5.1 hosts have ver A2, the OpenSM box has a ver A1 and the san has a X-2.
I had to remove the Mellanox ESXi vib and then reinstall it as it did not 'see' the A2 card. After the reinstall the card popped up and the targets were available.
It also seems that ver A1 will not work with VT-d (passthrough). After assigning the card for passthrough on the ESXi host, rebooting and then adding the card to the Windows 2012 Ess VM as a PCI devce, the VM will not start. It produces a caught error (at least not a PSOD). I have not yet tried with the A2 version.