I've shot and witnessed quite a few elk being shot over the last 20 years. Just when you think you have them figured out, you get one that really makes you scratch your head. I think the bull you shot in the shoulder was injured, but just shoulder damage. It's surprising to me how little they can react to such a hit. If the bullet just blew up on the shoulder without breaking the joint, you may not have been able to tell, and he probably would have bled very little from the entrance hole. If you get the same shot presented again, stay out of the shoulder, and double lung them. I don't really like neck shots myself, kill zone is too small, but a 50 yard shot is certainly doable.
As far as the 308 on the cow goes, well she was already running full out when you shot her, so she already had a full load of adrenaline and oxygenated blood pumping through her system. You pretty much have to hit them with a school bus at that point, if you want to see a "bang-flop" reaction. The 308 is more than adequate for elk, but it is NOT a school bus. You should have known you hit her well, when the first shot turned her and stopped her from running. I would have shot the second time also, just for insurance purposes. My father has used a 308 for over 30 years. It kills them, but very rarely does he get a "bang-flop" reaction, even when they are solidly hit.
My favorite elk poison is my 338 win mag. I have no problem breaking down both front shoulders if the shot is there with that caliber. I sure wouldn't try it with a 7-30 or 30-30, but double lung them, and you'll be tagging an elk.
Good luck and good hunting