So, I have finally removed Auto-Armour from some of my classes.
Now I am wondering - apart from the fact that one module slot has been freed, are there any other advantages to this? because it feels like it is a severe drawback to be an easy target for 1HK weapons. Does anyone else not use Auto-Armour and why?

I don't use it because it's the silliest module of them all. Sure, now you are a victim of OHK weapons, but you gain way more skill, and actually let those who would otherwise kill you, actually kill you.

I stopped using it, because 3 module combinations are more powerful then 2

I've been 1 shotted maybe 4xs this entire game, i've never ran AA for a second. If your getting one shotted, you are making way to much noise, and simply, you are not playing correctly. Any Crysis 2 (cough), most Crysis 2 players find its stupid how a basic tactic is automatic, its as silly as saying "can i run a nametag hacks, because i dont want to be caught of guard...."

AA was never overpowered for new comers in any way, they need training wheels, and i could understand why, however is annoying to see high level players use it.