They combat Daemons, more specifically. And if there are no Daemons in this game, the Grey Knights have to business here. They're elite and only go were they are really needed. It would betray lore if they were in this game.
Inquisitors aren't in the game so no need, also Wraithguards, Meganobs, and chaos termies could all be equivilant for gameplay.
Grey Knights are a seperate faction to space marines in the same sense the Imperial Guard and Sister of Battle are too. Forget what you have seen in video games previously where they have been an Elite choice. There sole job is to fight Daemons, so there is no point them being put in game. They just would not be in this fight.
The whole problem is they have no purpose except to kill the greatest daemon threats, their mere presence is suppose to be an endgame. Them just sitting back somewhere for appearance sake is underwhelming for them. I'd rather just see SoB.
Hmmmm i suppose... but (correct me if I'm wrong) isn't there something about after a while the battle changes to a different world? so say chaos is winning the final battle for the world, Grey Knights step in 'cause they obviously gonna be watching to make sure no super daemons be appearing.
This is where the lines Blur Chaos Marines and Chaos Daemons are seperate factions too and Grey Knights fight the Chaos Daemon side while normal Astartes deal with Chaos Marines.
More then likely the inquisition would call for exterminatus first, barring a daemon primarch or the greatest of daemons appearing Grey Knights would probably be somewhere else, maybe having them for like... an anniversary event or something but... it just becomes fanwank at that point.
I have to say that I would love to see Grey Knights also and there realy doesn't need to be any point to it they are just cool as hell. I know the lore behind them and like someone said the odd that even one grey knight showing up somewhere is just bizare but still why not.
