And you mark how many foes? And your basic attack on your charge does what? The knight could easily not fire up his aura and stance and do the exact same.
Exactly. What order the actions are performed will depend entirely on the situation of the combat, and what tactics you prefer.
If the enemies are bunched together, you could do:
Move - Move closer to the enemies.
Minor - Activate either Defender Aura or Cleaving Assault
Attack - Charge and make your MBA
In effect, this sequence provides about the same amount of defender marking as a PHB fighter with Threatening Rush. Now, we don't know whether the Knight has a punishing effect for those that violate the mark, so the monsters could simply shift away or attack another PC with the -2 without getting smacked. But I'm betting that the Battle Guardian feature will provide the needed punishment or stickiness in a simplified form.
This preview has some other interesting features. I was glad to see the Defender Aura doesn't actually Mark, and so it will not supersede another defender's mark.
But even more interesting is that Knights (and likely Slayers) gain more stances as they level.
I know one fighter that is going to switch to this build as soon as I can figure out what the other class features likely do.