I myself visited the "Kaon Under Siege" flashpoint many times over, so I had plenty of hints that some nutty professor wannabe had used the Rhakghoul virus to create a new strain of the plague, that he then planned on distributing through the galaxy. He tricked a little smuggler girl into carrying it to Kaon, in fact, where it was quick to spread through the local populace. Most of my Imperial buddies have a good time tossing that girl over a railing to her death, in fact.
Your complaints about the storyline are moot, imo. It's certainly well within the storyline of a fantasy-based science-fiction tale that a mad scientist could be playing around with germs. Heck, it happens in real life, too, right?
FWIW, it's always fascinating, to me, how players react to these sorts of events in MMOs. I've seen them play out before in other games, anyway. There're, of course, the griefers, who seem to delight in spreading the plague far and wide. Should've seen the ZG-virus-thing way back when, when Zul'Gurub first opened in WOW. There were some lowbies who utterly avoided well-populated areas, out of fear of virtually instantaneous death, complete with supposed blood bursts. Believe it or not, real scientific research has been done on such virtual plagues: read this
. Kinda makes me wonder how many researchers are watching us run around Tattoine hunting down infected Sand People and quarantine-fleeing refugees, hehe.
At least Bioware has provided some boon to the death this plague brings. Die enough times and you win a prize, lol.