Well, theres no way that we "need" anything in that department. But I think that they are a positive addition if added. Since you don't have this book, it might be difficult to draw the comparison without the material, but I'll try to do it briefly. And I know about a lot of things being worked on in this forum (ever so slowly), but that's another set of issues.
Swashbuckler
The swashbuckler is easier to talk about, in that it fills a niche often sought but difficult to pull off. Rogues and Fighter/Rogues are common classes to take to attempt to play a "swashbuckling" character using weapon finesse and such.
The archetype itself is easily satisfied with the core rules. Light armor, weapon finesse a finessable weapon, and stick to feats that enhance your abilities with the weapon and using it for varied tactics like Combat Expertise, Dodge, Mobility, Spring Attack, Improved Trip, and Improved Disarm. Skills need to be bulked up on include tumble, listen, bluff, and many others but the Rogue class should satisfy this. So there is no need for this class to simply satisfy the archetype, on this we can agree I think.
The problem is mechanical more than anything. Fighter/Rogues that try to favor this style have to rely on the rogues sneak attack most of all in order to be successful. But sneak attacking (actually attacking an unaware opponent, or flatfooted person) or feinting in combat are not necessarily what I percieve this sort of character doing. Even using Flanking seems out of character for the archetype. Other high level rogue abilities are interesting, but not exactly what most players envision when creationg such a fighter. The abilities of the rogue, while similar, do not tend to reflect what a player wants from this archetype. The fighter helps alleviate this through feats, but the fighter class is a bit too heavy handed. Modifying a fighter slightly does help though.
What the swashbuckler class does is create a direct path for a player to take a character through that does fit the archetype fairly well. It also gives benefits where a character would expect a swashbuckler to get benefits (dodge bonuses to AC in light or no armor, weapon finesse, combat expertise bonuses, and I need the book in front of me but it's at home...)
This is all IMHO obviously.
The Hexblade is less of a fit though. It is meant to fulfill one type of fighter-mage archetype that has a lot more "fight" in him than the bard. However, the Hexblade is definitely not as precise a fit to an archetype as the Swashbuckler is. It helps to satisfy the "forever cursed" character or the Fighter-Mage, but neither is as common as a swasbuckler. They mirror the Paladin but changed around (instead of smitting, they curse; instead of an aura of resistance, a 12th level hexblade gets an aura of unluck; instead of gaining a flat charisma bonus to all saves the hexblade gains resistance specifically against spells).
Here are some Hexblade abilites I have on my comp:
The hexblade can include his charisma bonus on saving throws against spells and spell-like effects. Once per day, as a free action, a hexblade can unleash a curse upon a foe. The target must be visible to the hexblade and within 60 feet. The target of a hexblade's curse takes a -2 penalty on attacks, saves, ability checks, skill checks, and weapon damage rolls for 1 hour thereafter. A successful Will save negates the effect. A hexblade can resist magical and unusual attacks with great willpower and fortitude. If he makes a successful will or fortitude save against an attack that normally would have a lesser effect on a successful save (such as any spell with a saving throw entry of Will half or Fortitude partial), he instead completely negates the effect. An unconscious or sleeping hexblade does not gain the benefit of mettle.
But, as I said, the hexblade is just more of an "interest" class than a niche.
