Remember when we first saw Mathilde travel in pitch darkness using nothing but her Magesight? IIRC it was when we scouted all those snotlings on the way to K8P (
link), and while she was prefectly able to see there was a time delay to her perception. It's why
@BoneyM vetoed galloping through the Underway at full speed on a Shadowhorse : she'd smash her head into a stalactite before it registered to her magesight. She hasn't shown significant range imitations on her magesight before (she's used it from one side of the valley to the other during the battles against orcs), which suggests that the problem really is a time delay. Maybe this is because the Winds don't perfectly mirror reality, maybe it's because she needs time to interpret what she sees, etc.
I predict that seeing through Pall of Darkness will have similar issues : sure she can see through it, but not well enough to be very confident while fighting. And of course it's even more of a problem for her opponents who have to wave their swords around at random hoping to hit her - but she can no longer properly block if she can't see their weapon's movements in time.
So it's a good solution, but it won't always be a perfect auto-include in every single combat situation.