I'm in pretty much the same boat as you are. I have a slightly higher ATG squat (1.6x bodyweight), but I also have a 2.5x bodyweight deadlift. While I don't have any solid answers for you, here are some things that have been pointed out to me by more knowledgable people.
A big deadlift doesn't necessarily mean that you have good posterior chain strength. There are plenty of ways to deadlift incorrectly. For example, I still currently deadlift with my hips a little too high when I start. This means that I don't really use my hamstrings and am pulling mainly with my lower back. I know that technically you shouldn't be able to stiff-legged deadlift more than you deadlift, but if your hamstring strength sucks, you will. So, although you do have a good deadlift, it doesn't say whole lot about your squat unless your form is spot on.
It's also generally more useful to know what exactly goes on during a squat, since you could have a weak squat for any number of reasons. For example, when I squat close to max, I tend to tip forward and sort of "good-morning" the weight back up. I don't know exactly what this means (I'm guessing weak glutes and hamstrings again), but it'll help others if you state that. One way that I've tested for "creative technique" when squatting is first squatting with a heavy weight that I know I can do with good form. Then I squat with a weight close to my max. In an effort to get the weight up, my body will do some funky stuff. I can finish the rep, but I'll certainly know that something went wrong.
Also, as a previous poster said, it never hurts to train your abs/lower back/quads/glutes/hamstrings in order to get your squat strength up.