It's all fine and dandy keeping good form with with what appears to be pretty light weight for you, but I do believe you need to get closer to the point that your form starts to break down to really...
I train traps directly on both shoulder and back day. I notice they are significantly more sore after back day which leads me to believe my back training indirectly hits traps harder than my shoulder...
This is how I train nowadays. Mainly because I don't need a giant bench/squat. It really is dependent on your goals and how your body responds to direct/indirect work. Well maybe.