You may wanna edit this in Valus taurac? Whatever the name go straight up and to the left crouch there ads his rockets will miss you about 80% of the time, you just have to worry about his machine gun and the enemies that spawn behind you which aren't many. Obviously when he moves you move though there's a second balcony on the other side. Also angle high enough to throw grenades from cover, you have to get good at that but it's possible.