I use FireShot to capture the entire page, then paste it on PaintToolSAI (you can use Photoshop or even Paint, doesn't matter) and then crop, takes very little additional time.
But you have to be used to the shortcuts to make it efficient, the cropping process doesn't take me more than 20 seconds, which is faster than manually setting the box around the area I want to screenshot with a dynamic scroll where I have to be careful about not overscrolling or whatever.
