Actually whats probably knocking your weapons ofline is the thermonic torpedoes, they spam you with them, (i've never seen them use subsystem targeting btw), they each have a chance to drain 25 power from weapons and engines. The Detructible ones are a garunteed -75.
As for tet procs. the base is somwhere around 400 for us. Most NPC's get significant modifiers to weapons damage. 5K sounds like somthing a bit more, but still it would explain a lot.
They use subsystem targeting on weapons constantly.i was debuff hawking trying to figure out how to negate it, and it's a beam target subsystem.