PhelborePhasing Sequence is an Experimental effect that does slight damage through shields. There's no defense, but it does drop 10% of the weapon's base damage. I'm not sure if it'll do module damage, the description is unclear.
So the weapon does 10% less damage, but penetrates shields? Well that explains it then. Wouldn't take much from a rail gun round or that plasma gun, to do enough module damage to take it out.
For 10% less damage but not having to bugger around with the ai's incessant use of shield boosters, I'd figure this sort of experimental engineered effect to be almost standard... I was actually contemplating not even using a shield with my vulture, while I was figuring out how I wanted to assign those optional internals. Now I might do it even more. Then I could put a internal module reinforcement package on board to help protect the buggers.