Hey Gektor,
I finally got a chance to try this again in my lab environment. I can confirm that pfSense 2.4 release properly detects and can use the passed-through NIC for me. However, I will note that things are a little wonky, I suspect the pass-through is confusing the Broadcom driver, as it doesn't put the interfaces up on boot. (However, manually putting them up and running dhclient worked for me.) I did not test very extensively, so I imagine they won't come up when booting after install either (I did my testing from the recovery shell.)
Looking at your screenshot, it looks like you're having some similar driver problems (which is different from my original issue.) Your Intel NIC is seen by pfSense, but it fails to initialize properly. Do they appear in your ifconfig output? If so, you might manually putting them up manually (ifconfig <device-name>up) and configure them (dhclient <device-name>) to see if they work. However, based on the fact that it kept using en0 for each port, I suspect they won't appear.
My gut says that the PCIe passthrough is confusing the Intel driver. Hopefully it is something the FreeBSD developers are aware of and it will be fixed in FreeBSD 11.2. I don't have enough time to investigate my specific issue further. Since you have an error in your logs, you might be able to find out more about the root cause of yours.
(EDIT: Removed brain fart involving FreeBSD versions.)</device-name></device-name>