Yes, i lost a few planets to the AI.

I thought it is quite a bit to good at finding my undefended planets and sneaking invaders there. But it is an early game problem, the AI isnt good at keeping up with the soldiering techs.

After a few soaks, it becomes clear that while the AI does invade, it doesn't do it very much or very well.

I regularly see stats screens at the end of 400+ turn soaks where the AI has colonized 100+ worlds, managed to build 2000+ warships, has fought 1000+ space battles, has taken and inflicted staggering losses... but has only actually bothered to invade 4-5 planets in the whole game. And that's the successful, aggressive AIs. The peaceful or weak ones never invade anything. 

There's a good reason why. The AI only invades something that's within a certain radius of its Transports, and by default, that value is 8, which you'll notice is extremely small, especially on large maps. Increasing this radius makes them far more aggressive at invading, and the Drengin notably become monstrously powerful, because they tend to go after the high-level Kinetics techs very early. 

I've made a mod which fixes the AI.

I haven't noticed the side-effects of setting this value too high. I'll keep experimenting. So far, the value is only at 16 in my mod, but this does mean that it sometimes leaves transports idling next to its homeworld once it gets big enough, unless this faction is located in the center of the galaxy, in which case the center faction tends to be by far the most successful.

What needs to happen is this radius of aggression needs to calculate distance from the AI's borders, rather than from the transports' resting spot. That would fix everything. That's up to the devs to fix, however.

Normally I would agree with you about the Drengin going for Kinetic weapons and armor But in a game I have going atm they've concentrated on Beams and shields which suits me as I've just built all frigate fleets.