There really shouldn't be many scoiatael units since they were kinda sorta disbanded after the war (book one). You could make the argument that Nilfgaard tried to put them back to work, but after the peace of cintra and what that entailed in regards to the scoiatael and their more prominent commanders, i doubt they'd be willing to do their dirty work for them again in order to destabilize the northern kingdoms. (and game story-wise we know that the.. "former" Lodge's actions along with the "double agent" Kingslayers is what led to the destabilization this time, Iorveth's unit just happened to be in the right place at the right time to advantage of). So yeah, im glad they don't have a big presence, it doesnt fit the lore at all. (you can say the same about the overabundance of monsters in the world - they are supposed to be near extinguished thanks to the Witchers (also why there aren't many Witchers left or being made any more) but at least that serves a gameplay purpose, who'd want a game world without all the monster enemies right?)