Eh, it is implied that every Ark Mechanicus (at least the old ones) is like that to some extent, so there is at least two of them.
And no, they weren't made by C'Tan or Void Dragon, since they're actually the thing Mechanicus are looking for - complete, self-updating STCs in ship form. They represent the peak of Human technology, which really looks like it was way more advanced than even Old Ones/Necron stuff.
EDIT:
I just noticed I haven't actually posted this:
Well... outside sheer numbers Star Trek has a higher level of technology, weaponry, and shields.
Warhammer isn't so much "Overpowered" as it is vast and "EXTREME"
As for Imperium, sure, Star Trek proably has better tech (except for weaponry, I am not exactly sure). As for others... I am convinced that Necrons would genocide Star Trek and cackle mechanically whille doing so.
And while I have no actual idea what Rifts, but it sounds like it fucks any suspense of disbelief sideways.
It has more to do that the technology in Rifts has advanced to the point where things have started to sort of break down. A ordinary pistol in Rifts could take down aircraft carriers in 1 maybe 2 shots.
I am pretty sure that no technology is or ever will be possible that allows to take down an aircraft carrier that fits in a pistol-sized package. It can't even be rationally handwaved, really, unless said pistol is just a remote detonator for ridiculous amounts of explosives inside the carrier or something.