For my Alliance arcane mage, I am recommended Fen Spirit Headdress for BIS but it is not my faction rep vendor so how do I eliminate this choice?
You can get some versions of it as alliance I believe… up to whatever item level world quests will reward. You can also exclude specific items when running Best in Slot.
I can add to the list of things to do to create some more filtering of which versions of world quest items can be obtained by different factions.