are you doing the exercises in that order? if so i would say put rear delt work towards the end, exhausting the rear delt takes away your secondary/ support muscles when overhead pressing, id say do an exercise to warm up the front and laterall delts then move into pressing, anything after that then rear delts last, thats only my personal opinion though.
personally for delts i grab some 15lbs dumbells and do half laterall raises towards the front for a warm up, moving into dumbbell or barbell press then heavy laterall raises finished with 3 sets of 60 reps reverse flys for my rear delts, i do 2 sessions per week on shoulders but only train rear delts once on my heavy pressing day for chest, allows for that great pump and on my lighter day i do dynamic movements for shoulders, everyone seems to struggle with rear delts and i did for a while till i did huge reps on them, started gaining size and strength in them went from doing 10lbs to 25lbs for each set, obviously with pauses and such for rest towards the end of the sets etc but its worth it and really pumps up the whole shoulder, just make sure youre leaning on a bench otherwise that lowerback will get sore...