Yes, you are overlooking some major flaws
I'm only going to address the Major Flaws you're concerned with, since the rest is subjective to both your game play and how people play the class. This should help you get through at least a couple of misconceptions you have.
- Pact Weapon (PHB. pg 108) - You can only have one of these, and due to that, Thirsting Blade can only be used with your one pact weapon. If your DM does happen to allow you to take two pact weapons, that's cool, but is clearly a house rule. Make sure your DM knows about the wording of Thirsting Blade with respect to Pact Weapons.
- You have only one bonus action possible per turn (PHB. pg 189). If you have many abilities that use the bonus action (Cunning action, offhand attack, specific spells, etc) you have to choose which ONE to use.
- Survival wise - largely dependent on magical item availability, your feats, and potion use. If you take fighter at level 1, you'll have higher hit points to start, but your saves will leave you mentally vulnerable. That's why I recommend Archfey pact below, to remove that problem.
The following part is only my opinion on the build itself, and where I would make changes to better fit your stated style of play.
Personal build recommendations:
- Take 3 levels of fighter to become an Eldritch Knight so you can have weapon bond (two weapons bonded, functions very similar to Weapon Pact, allowing for 3 summonable weapons.)
- Instead of Fiend, use Archfey as patron because the up close abilities and immunity to charm are superior for an up close fighter. Especially since Misty Escape gives you a free exit in overwhelming situations.
- Feats - Heavy Armor Mastery, Tough.
They are special nonmagical techniques based on being a scholar of combat. This is explained in the Battle Master entry:
Those who emulate the archetypal Battle Master employ martial techniques passed down through the generation. To a Battle Master, combat is an academic field...
Individual maneuvers explain what you're actually doing:
Commander's Strike: You can forgo one of your attacks... to direct one of your companions to strike.
Goading Attack: You can... attempt to goad the target into attacking you.
In each case, you're mundanely directing your ally or goading (through voice or gesture or just annoying attack placement) your enemy. You're just really good at it because of your battle mastery.
Although I can't find a reference in the PHB, it's generally accepted in D&D that you're doing more with your turn than your single attack. Your PC might constantly be feinting, dodging, making threatening jabs, and so on. Your attack rolls represent those actions that are actual opportunities to do damage. From this perspective, then, a Commander's Strike doesn't mysteriously make your ally move faster; it just gives them an extra opportunity that they otherwise might not have had, just like a retreating enemy lets them make an opportunity attack.
In the games I've played, these maneuvers have been explained however seemed appropriate in the situation and were never assigned advantage or disadvantage, but I don't see a problem with the saves being modified in unusual circumstances. I'd just make sure that you're treating other players' unusual abilities with the same level of scrutiny.
P.S.: The Battle Master is, in part, 5e's version of the Warlord class from fourth edition. That class has the Martial power source, indicating that it's wholly nonmagical, with the following explanation:
You have become an expert in tactics through endless hours of training and practice, personal determination, and your own sheer physical toughness.
Best Answer
There's relatively limited ways to optimize maneuver choice for two-weapon fighting relative to other fighting styles, and the optimization is minor at best.
First off, to note, you still have the same size maneuver dice pool as someone doing any other build. You won't be able to use more maneuvers than other fighters overall, but you will be able to use them more quickly (or reliably, in the case of maneuvers that require you to hit first) in any given fight due to your additional bonus attack, since maneuvers are limited to one per attack (PHB p.73).
As such, any following statements I make on the effectiveness of a given maneuver are purely relative to its effectiveness in a different build focused on doing less attacks, but more damage per attack (as doing more attacks for less damage each is two-weapon fighting's niche). I'm not saying any given maneuver is bad, and you may still find a place for it- since you end up with 9 total maneuver options by 15th level, you have room for some utility/flavor picks rather than "optimal" ones.
The Bad(...ish)
The main benefit of a two-weapon fighting build is the one additional attack on each of your turns, at the cost of a bonus action- and bonus actions are limited to one per turn. Therefore, the maneuvers that require the use of a bonus action- Commander's Strike, Feinting Attack, and Rally- are going to be hard to find a place for, as they come at the cost of your offhand attack.
Since you're going to be doing more attacks for less damage, Precision Attack (which only adds a bonus to hit for a single attack and no bonus to damage) has less value for you than others. Similarly, Riposte (which only lets you make one additional attack as a reaction) has less value.
The Good
Many (but not all) maneuvers use the superiority dice roll value as damage in some way, shape, or form. The ones that do are virtually all effective for you, as you have the option to quickly burn through your superiority dice to use these maneuvers' bonus damage since you attack more frequently. In addition, since you attack more often, you'll have critical strikes more often- and since for many of these maneuvers you choose to perform them after hitting, you can choose to expend them after seeing you have crit for double damage dice.
Now, many of them have secondary effects that don't do anything extra with repeated uses on a single target if they're already affected by it, such as Disarming Attack and Distracting Strike. That might not be too much of a consideration if multiple different targets are in reach or they successfully resist the effect on the first attack(s) (and, of course, you can switch between different maneuvers with each attack against the same target if you land one with a non-stacking effect).
Of the maneuvers that use the superiority dice value for damage, I think the following are of particular note:
Trip Attack is useful as you can attempt to knock the target prone on your first attack of the turn, then get advantage on the prone target for all your remaining attacks if you successfully knock them down. This is especially nice if you're burning superiority dice for damage on followup attacks- you have a higher chance of a natural 20, and you can roll double the superiority dice damage on a crit. Do keep in mind who else gets to go before the target gets a chance to stand up- it'll hinder ranged allies making attacks against the prone target, and help melee allies.
Menacing Attack has the potential to be incredibly powerful in boss-style encounters. If you can make the boss creature Frightened of you, they'll have disadvantage on all ability checks and attack rolls while you're within its line of sight which is a tremendous defensive boon to your party until the end of your next turn.
While not as powerful as other status effects like Restrained, Stunned, or Paralyzed, Frightened is still the kind of status effect that might make DMs burn Legendary Resistance charges for creatures that have it and rely on melee attacks, and you have more chances to land it than other fighters. The movement restriction portion of the frightened condition is mildly less useful since you're likely already adjacent to them, but if you move away they won't be able to chase.
Maneuvering attack can also be incredibly powerful in tactical situations. Since you attack more than other fighters, you can do more maneuvering of your allies- either out of danger, or into position.
Conclusion/My Suggestion
With your starting 3 maneuvers, Maneuvering Attack, Trip Attack, and Sweeping Attack are versatile tactical choices covering assisting allies, killing smaller/weaker creatures, and controlling individual stronger ones.
Once you get additional maneuver options at level 7, Menacing Attack would be my first choice. By 7 you're likely starting to occasionally fight bigger monsters that Trip Attack might not work against as easily. Some of them will have multiattack, which the Frightened condition is very nice to have against.
Other than that, I genuinely think any two-weapon fighting focused maneuver "optimizations" are so small it'll be easily outweighed by filling in whatever tactical needs you've discovered your party has as you've fought alongside them- heck, the above optimizations are so relatively small that's likely true from the get-go.