The big one is that while Robert Jordan was a veteran and graduate of the Citadel (a military college), 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, an 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...
Seinfeld Is Unfunny: Nowadays, The Wheel of Time is considered by many to be a horrendously cliched example of how all fantasy books are too long, with series that go on seemingly without end and yet little happens in them. When the first volume was published, in 1991, most fantasy novels were actually quite short, and/or tended to be trilogies or quintets at the very longest. However, he inspired so many other writers to pad out their volumes and stretch their stories over ten or twelve volumes that by the 2000's he tended to get lumped in with those he inspired, often cited as the Ur-Example, but rarely acknowledged as the man who started the trend.
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.
Originally, there was going to be a fourth Two Rivers boy in addition to Rand, Mat, and Perrin. The character ended up being largely peripheral, and Jordan's wife eventually convinced him to drop him.
This is actually referenced in-story when the young man in question, Dannil, muses to Tam early on in the Battle of Merrilor what would have happened if he'd gone with the three main heroes when Moiraine took them out of the Two Rivers.
Robert Jordan initially planned to write at least two more prequels (one about Tam, and a second about Moiraine and Lan), as well as a sequel trilogy following Mat and Perrin several years down the line (collectively, fans tend to refer to these as "the outriggers"). Unfortunately, Author Existence Failure hit before Jordan produced much material on any of them, and it looks like they'll probably never get written at this point.
There was originally going to be a subplot in Memory of Light revolving around the Sharan leader Bao the Wyld better known as Demandred. Unfortunately, it threw off the pacing and forced Sanderson to do a lot more worldbuilding than normal, since Jordan hadn't left a lot of material on Shara. It got cut from the book, but ended up seeing the light of day as the short piece River of Souls in the Unfettered anthology.
Word of God: Robert Jordan, occasionally putting long arguments to rest... when he didn't point the finger at RAFO. See Jossed.