I remember the first time i met the Khan, after i bought the dlc: it appeared really early, when i had fleets like 10.000 all together, maybe in the year 2250, or so. And as one of its fleets had about 25.000, it was a real threat, as it had several of them. I was barely being holiding them at bay, at one system with a fortress, all my fleets and the mercs i could rent from others. And that only, because they never send two fleets at the same time.
In my game now the khan appeared at around 2300.+ I cannot recall the exact year, but i was just preparing to attack an fallen empire, having like 500.000 strenght. And then the khan appeared, with its fleets of maybe 100.000 all together and i could only sit there and ask myself, "wtf?".
Even as the khan attacked my allies, i did nothing. i wanted to see, how it works. And it had some success at the beginning. But this late? At some point one of the empires took some bigger fleets and attacked, and that was it.
Something is really wrong with the time-balance in this game.
(Beside of all the other stuff, like that the constructor-ships of the Khan trying to fly into occupied systems.
Or that do not understand, that their occupying systems is different then that of "normal" empires: if they attack a system with an inhabitat system in it, and then go out again, the "station" comes back to life. An constructor then trying to fly in to occupy the system gets shot down then.
Or, that the wayfinding is kinda mess: trying to reach a system, which is close by, but only accessable via a looooong way-around-path resolves in sending ships all the way through unoccupied systems.
In general, everything there is broken as hell. Paradox should be ashamed of themselve!)