I think both tim and
storm have good points here. Just because you arent feeling it in your lats doesnt necessarily mean they arent really being hit, and also that its quite possible that its your biceps which are the "weak link" in these compound movements and so letting down your back from getting in a decent workout.
I find with women, and even most men who are new to weight training that they will always complain when doing lat pull downs, assisted chin ups and other such back exercises that they predominantly feel it within their biceps because their arms are quite weak, all this being with excellent technique used throughout.
I think there is not really much you can do about this problem except to continue training as you are, and possibly even look to strengthen the ligaments and muscles of the upper arms through some isolation work like bicep curls and getting them used to lifting heavier weights that your back is capable of pulling.