The big one is that while Robert Jordan was a veteran and graduate of the Citadel, Brandon Sanderson has problems with battles and combat in general. In A Memory of Light, the forces of the Light make glaring mistakes that aren't explainable by the corruption of the high command. The forces holding a pass are mostly cavalry, while the forces fighting a rearguard action (in a forest!) are mostly ranged (with artillery!). The forces for an assault on (and subsequent defense of) the enemy main base are, a good part of them at least, irregulars without real equipment and supply. Also, a often used tactic for cavalry assaults is to rip the ground apart before they hit, as to make sure the horses stumble (in an assault!).
Another is usage of military organisational units. One commander thinks how good it is that she has two whole banners of crossbowmen, which would be any number from 100 to 1000 (at the most), in an army numbering tens of thousands, fighting an enemy with one or two hundred thousand soldiers...
Shrug of God: Jordan's stock answer to many things was 'RAFO' - Read And Find Out. Also the official stance toward the conclusion of the series—Word of God is firm that anything that happens after the final page is strictly up to the reader.