During normal braking, you are not taxing the system that hard so you don’t really know that all is well. What you think is only 30-40% of your braking capacity might really be closer to 80-90%. Under emergency conditions, you find out that the brakes really aren’t up to par.
I went through this on our 86 Tercel a while ago. It got totaled before I figured it out, but I recently did the brakes in my truck. I used the same pads that I have always relied on, and they just don’t work like they used to. These are the same pads I used on the Tercel so now I suspect the pads that I have been using all these years have suddenly dropped in quality. BTW the truck is Nissan with rear anti-lock brakes similar to your Dakota.
It could be the master cylinder or booster, both are expensive experiments. I’d go for the master cylinder first, but I think before that, I would suggest that you try some composite brake pads that use Aramide or carbon fibers. These have better grip than either semi metallic or ceramic pads.