Uggh. This topic comes up periodically, with folks suggesting fighter BAB and HD as the way to fix some perceived inadequacy. If you think this, then I gotta tell ya, you're suffering from some kind of disconnect here.
Maybe it's a perception that any character proficient with heavy armor and martial weapons is de facto intended for a career in front-line melee (after all, if it doesn't cast nukes or heals, what else is the point of it?) . Maybe it's the notion that a character can't be effective if it's a lackluster damage-dealer, that all classes should pack a whallop (and those that don't are therefore weak).
Whatever the case, please understand the simple truth: the marshal's role is to buff the party. The marshal kicks butt when he's helping the entire party kick butt. Put aside those notions that huge bursts of damage define effectiveness, With the marshal, it's about small, persistent bonuses spread out amongst several people.
Does giving it more BAB and HD, make it better at buffing? Nope, it's just a DM trying to make it into something it's not designed to be (a fighter analog). Any criticism of the marshal or suggestions about how to improve the class should stem from whether or not it is an effective buffgiver, not whether it's a great tank or melee superstar.
I'm glad to see at least some folks in this thread understand that. The marshal is lacking IMO as well, but the fix comes from making it better at its intended role. Here's why:
1) Its minor auras are mostly rubbish.
2) Only one minor and one major aura can be active at once. How many can you get before you just don't need any more? I'd say three of each.
3) Grant Move Action is a great ability (thoroughy underrated), but it doesn't gain enough uses to really offe rmuch appeal.
4) Here's the biggie: it offers a player nothing to do in a given round other than turn the spigut on its auras, which is a swift action. There need to be some tactical actions available.
I know adding BAB, hit dice, skill points, and save bonuses are the quick and easy fixes, but resist the temptation and just figure out what would make the class a better buffer. For me, it would involve:
1) Allowing certain minor auras to work in unison, or even collapse some into one. There's no great reason a bonus to Fort saves and a bonus to Con-based skill checks (all one of them) should be two separate auras.
2) Grant the class some feature that is based on making a tactical decision. My basic example is allowing the marshal to designate one ally every round who gets an extra bonus from the auras.
3) Give it some ability to remove debuffs. A marshal's job is to rally the troops, after all.
4) Give it some higher-level, capstone features to work towards. Maybe it can eventually grant either a move action or standard action.