As for increasing threat generation on all targets, regardless if you're firing on them, I have yet to see any information on this. Going by the wiki (http://www.stowiki.org/Skill:_Starship_Threat_Control), it simply increases the threat generation value per weapon hit on a single target, not targets you aren't firing on. If you're using a Torpedo Spread ability, well then I could see why you grabbed aggro on
Aggro is generated as an accumulating number, on the primary target first, then the other members of the spawn. Once aggro is gained it increases as a generated number that increases as damage is done. That is why threat mechanics work to reduce the aggro number or score towards 0 or upwards to infinity depending on role. STO, other than placates, doesn't seem to have a threat lowering role mechanic, only a threat increase mechanic. Once that spawn knows you are a threat they stay that way until someone else gets that aggro, steals it by out scoring you on threat, or you leave the spawn alone and it resets.
This is why high DPS and spike damage can cause escorts to steal aggro from a designated tank. IMO, its this poor mechanic that is the cause of much of the escort cruiser angst. But that is another subject.
Chingachgook told me, Don't try to understand them; and don't try to make them understand you. For they are a breed apart and make no sense.