Pre-reqs
I dislike alignment requirements, but that's more personal taste than anything.
Intimidate 9 means you're probably Hexblade 4/Marshal 2 before entering. You only need Hexblade 1/Marshal 2 to get the specials down, but Mettle and the Dark Companion ACF are both very delicious for Hexblades.
I can't find the Frightful Presence feat. Draconomicon has Awaken Frightful Presence, but that requires you to be a dragon to get it. Similarly, Races of the Dragon has a couple Draconic feats that emulate a very weak version of Frightful Presence, but doing so requires upwards of two feats.
For a replacement, you could go with either Imperious Command (Drow of the Underdark) or Dreadful Wrath (Player's Guide to Faerun). Honestly, I'd say go with Imperious Command or something else like Skill Focus: Intimidate. If it wasn't for the stupid type restriction on Awaken Frightful Presence, it'd be perfect.
Just found the feat
Frightful Presence. Carry on.
Skills, BAB, etc.
Good BAB is nice. D10 HD fits. 4+INT on skills helps. Good Fort/Will does, too. Full-casting is very nice, but it is most likely going towards Hexblade casting, so no worries.
Aura of Dread is very nice. You should give an example character's bonuses, just for clarity's sake.
Inspire Terror should probably have a minimum uses per day (Say, X+CHA mod) where X increases with levels. Twice CHA mod scales in an odd fashion. Inspire Focus has the odd effect of "turning off" your marshal abilities. I'd recommend tweaking the wording so the Dread Commander can still rally his troops. Inspire Eternal Servitude is a silly capstone. I like it, but you should mention limitations on how allies can be raised, how many HPs they come back with, etc.
Armored Mage is a solid class feature, if a little "bland." You should mention if it works on shields or not.
Fear Immunity fits. I like it.
Choke out the Weakness is incredibly silly. Most of those effects make sense to remove, but
prone caught my eye.
As is, trading attacks for removing debuffs is amazing. You should mention if there is any limitation on uses per day or what not.
Arcana of War is interesting. I know
Races of Stone has a feat that circumvents needing to cast defensively so long as you have a shield. This class feature just ignores the shield (and the damage, kind of) and casts away. Not bad.
Incarnation of Terror is mostly filler, but solid filler for someone with any amount of Intimidate focus.
Harbour no Traitor is basically +yes to Sense Motive. The flanking immunity bit is odd, but I like it. Maybe require the "know all lies" bit to be against targets affected by the aura?
Greater Aura of Dread is nice for the increased range. The debuff seems a bit too situational, mainly because Hexblade spells are going to have a fairly low save DC.
Terrifying Entity makes me want to grab the
Goad feat to force people to attack me.
On that note, maybe throw in a penalty to attack the Dread Commander even if they succeed or in the odd case where there are no other targets.