So getting Anatoly to help him stop Prometheus blew up in his face, so now he's going to get Slade Wilson.
Is Oliver trying to cause himself more trouble??!!!
Yes, I really cant see Deathstroke's aiding Oliver not blowing up in his face.......unless Oliver puts some type of poison in him or a bomb or some of Amanda Waller's explosive nanobots.
As to Prometheus, well he has basically made GA public enemy number 1, sabotaged Oliver from within, planted a mole in Team Arrow, had Oliver abducted and was badly tortured and had his tatoo's fried off with a torch......so while Deathstroke killing his mother was very bad, what Prometheus has done to him is about as bad.