It depends if you actually have those 3 proper raids a week, does your guild often cancel raids or are you often missing/switching/pugging people?
My guild is supposed to raid 2 times a week, but often someone cant come or has holiday or just doesn't feel like raiding, we average at around 1 raid per week and also often start late, so instead of progressing more, we just clear ToT (2/13) on one day.