Oh my god, those little smileys are so associated with Yuu I think it's his face. Every time I make a post... He's watching me.
That's not necessarily far from the truth now isn't it?

I hope you can answer these questions in great detail. Looking forward to any future info on everyone's favorite non-avian purple soldiers! 
Mind = Blown
I... What... How did I not see that before?
(the rhino-beetle Thespians travel the old fashion way, and they don't see the problem with crossing galaxies)
I almost spit out my drink!
It seems morning stars aren't the only massive balls hanging down from a Graidient's exoskeleton.
Here's a good idea from Mass Effect: Most star systems in the galaxy haven't been fully explored, so "bounties" are paid to anybody who's willing to do so! That opens up a nice big economic niche for travelers.
Don't we already have that, which is kinda why tracking pirates and other assorted threats pretty difficult?
Also, I seem to recall that there's a quadrant that's barely been explored at all. It's home to Darth Greivi's peoples, the lower right quadrant?
but surely that must be their only ship.
In that case, I'd have to say sorry...
>_>
It's far, far more mind-bogglingly colossal than it needs to be already.
It's basically a glorified yacht created by guys with technology somewhere between the Culture and the Xeelee, and retrofitted for military use.
It's designed to be big.
There's also the fact that they need to be big to store all that processing power. Crossing the voids between filaments is pretty hardware intensive, after all. And that's not factoring in the people with equally big ships that are, for one reason or another, all out to get you.
Hell, it has no defenses!
It does.
Particle barriers, phasing out, space bending, EM barriers, hyperlinks (aka judicious use of portals), surgical precision particle barriers, among others.
There are absolutely zero ways you could conceal that monstrosity!
Unless it phases out into another dimension completely or creates a pocket of isolated time-space, like some methods of FTL.
Also, being visible for everyone to see was kinda the point before they got commissioned for war.
If it's really that big, it could conquer the galaxy in a week!
Which is exactly what it does, when "They" aren't being drowned by Olympic swimming pools full of hubris at the time.
Or unless the galaxy in question also has Starships or things of equal threat.
It has got to be the STUPIDEST, MOST LOGIC-SPITTING-UPON thing this forum has ever seen! GRAGHFRAGHLBRGHLBAGGHL! WHY? DOES? IT? EXIIIIST?! THIS! MAKES! NO! *inhale* SEEEEEEEENSE!!
It does, it's just that it happens to be an Out of Context Problem for this particular galaxy.
Kinda like this guy.It also doesn't help that they're basically the "Boss Monsters / Dungeons" of the week.
No, apparently the Nameless have hundreds of these things, being created for whomever-their-leaders-are. Oh, and they launch hundreds of miniature versions of themselves the size of planets.
...
About a million, actually.
Though, considering the scale of the conflict "They" got themselves into, it's not really that much of a stretch.
And then you factor in the fact that, aside from defending "Their" territory against legitimately threatening enemy ships, "They" are also conducting multiple active expeditions going in all directions.
They're pretty stretched thin at the moment and are slowly dwindling in number due to attrition.
Oh, and don't forget some of their leaders are almost as big as the ships.
Only Bathariadne, who happens to belong to a different race, and as such really isn't a good comparison.
The biggest Atheim is only the size of a terrestrial planet, with everyone else ranging from moon-sized to skyscraper-sized.
I hate to hate, but there's a reason Anime doesn't work in these kindsa things.
I didn't base it on anime.
Though I shouldn't really talk too much, I am a major 40k buff and some of my stuff can be shot full of so many holes it makes swiss cheese look smoothe and solid. But still....
The Daemon Princes of Chaos would like to have a word with you.

....and we jumped all over that guy who made a star-system-size ship a while ago.
Because the tech disparity regarding the ship's size wasn't really conducive.
Now, if he'd stated that they had tech of a similar scale, or even just on the same level as Halo: Cryptum's Forerunners...
I've had issues with this from the start, the scale makes it totally impractical, realistically
Unless you're technology is on the same scale as some of sci-fi's heavy hitters.
I've had issues with this from the start, the scale makes it totally impractical, both realistically and roleplay wise.
You do have to remember that they weren't meant to be practical in the sense that player characters's ships are practical.
They're mobile dungeon levels, like Unicron.
They are literally designed to be taken out by a coalition of good guys either by overwhelming it's exterior or blowing it up from within.
Ship that size is unnecessary, for one. There's no reason for a single artificial entity even the size of a typical main-sequence star, a pinprick in the presence of a hypergiant like VY Canis Majoris.
See above.
A single death-star sized machine completely devoted to weapons power should be able to conquer an entire galaxy in itself, theoretically.
Unless the galaxy's security force contains ships the size of star systems, which is kinda the case with the guys the LACs are up against elsewhere.
That, and their original purpose aside, you'd generally want to pack a lot of stuff if your nation's foreign policy happens to involve travelling to places several billion lightyears away from home.
The only reason Talsenreave is as big as it is is mainly because it's gigantic cargo bay, living habitat and power requirements.
Why yes, that also happens to be some of the reasons why LACs are the size they are, mostly the power requirements.
Making a ship the size of "Majoris" would probably require the power output of the entire galaxy to function >_<
There are such things as artificially sustained supermassive blackholes.
There's a time where even the harshest nitpicking borders on common sense.
While I generally agree with that sentiment, some research and rationalization on the LACs would show that this isn't one of those times.
I mean, no offense to the Talsenreave, the thing is pretty awesome.

But, at least one of the reasons LACs, and Starships in general, are big is because traversing the universe is just that power consuming, let alone when you're trying to fight equally sized ships. Compare that to the moon-sized Talsenreave which can cross entire universes.