[quote=@Halvtand]
I think this looks really interesting, getting some nice F.E.A.R-vibes from this. 
I also enjoy that it is not simply a good vs evil-thing, order vs chaos is a lot more interesting and it really helps the setting that we have magic users in the GRAM and the mention of witches out in the world having established societies. 

However, magic is described as extremely powerful, a basic "do anything"-ability but with the fickle-rule applied to it. So I am wondering about exactly what a trooper (non-magic user) can do against a witch? 
[/quote]

Well, it is theoretically do anything... so it basically boils down to three factors that can affect a witch powers: talent, discipline and experience. You can cross the discipline bit, they are an anarchic lot. Talent is an even spread: there are monsters but the vast majority is middling. And experience, only few have enough of it.

The reason they ruined the world was less of the sheer firepower and more of the world descending into chaos all at once.

A normal GRAM trooper has discipline, teamwork, intel and material weapons at their disposal. It's safe to assume that a team can dispose without much problem of the average run-of-the mill witch as long as they are sensible and aren't caught on their back foot.

(I will allow PC troopers to be better than average. After all, they should be a viable choice.)

GRAM have also sorceresses and enchanted armaments if the target is tough enough.