The fae have a tendency to plot for years, and then cap it off with a sudden YOLO.Fair enough, I thought part of the reason that Molly had issues was that young fetches are so dumb they're barely sapient but I don't actually have a citation for that.
I'd like to say that the fae should know better than to play long term plotting games with a guy who at times who's "mysterious ways" can make a sane tzeentch look like a chump, but they have shown a willingness to try their luck.
I'd still buy almost anyone else trying this before the Denarians though. The closest we see them get to this sort of thing is with throwing that coin at little Harry and driving off. Whatever protection they're under is probably specifically set up for countering them, and Daniel hasn't done anything to take him outside of that yet.
Schizophrenic plotting is pretty standard for them.
As for the Denarians, look at what happened with Father Vincent.
Associate of Father Forthill, who is Michael's pastor, they kill him in a distinctive way with plagues, have Cassius steal his face and ID, use it to get a sample of the Shroud of Turin, then use his face to hire Dresden, another Michael associate.
And they still have the arrogance to abandon the body somewhere where it ends up in the Chicago morgue, imstead of simply burning it to dust with the magic we know every one of them can wield.
Arrogance is a defining Denarian trait.