I don't know if I'd agree that you need major help, because you already have FG which is half the battle.
As other posters stated, pulling 4 mobs at level 58 may be too many at your level, considering gear options as well. Using shadowbolt to drop them quicker is definitely a valid plan of attack. Also consider using HoT after DoT'ing the mobs, then shadowbolting them as the flee if you happen to pull more then you anticipated.
P.S. Don't forget, not that you were, to be using that HS in a pinch.