Seriously though, my gut tells me that the servers/instance might just be too busy to generate NPC interdictions as quickly as they used to... Sure, I still get the warnings, but now they just never show up.
I have a couple of stations I typically run missions between when I want to make credits. One has a crazy short arrival (10 LS?), the others are about 500 and 2000 LS. Prior to 3.0, stacked with missions, I could always get in to the close station (10 LS), and almost always to the middle station (500 LS), WITHOUT interdiction. However, pre-3.0, I had about a 50-50 chance of getting interdicted on my way to the 2000 LS station. Chance of interdiction always seemed relative to the time spent on arrival. It always felt to me that the servers didn't have the necessary time to generate the interdictions on the closer arrivals. Now, I'm hardly getting interdicted at all, even on a 2000 LS arrival. I probably played for 3-4 hours this weekend in these systems and only got interdicted once! (and yes, it was on the 2000 LS arrival)
BTW - These are all cargo delivery missions from an extraction station. So yeah, 400-740T of Gold, Platinum, etc depending on which ship I am flying...) usually topped off with a bunch of Sensitive Data Missions as well.