As for the seeker mission: it's pretty clunky, I'll admit. But I had it pretty much down after a while. When you get a green bar, I tend to scan the area in a circle by following the green bar. Get too far, and it'll become red. The bar isn't that precise, so if it shows you to a direction in front of you, it doesn't necessarily mean you need to go straight ahead, you can still go slightly left or right. I don't use the items that are meant to narrow the search since I tend to find what I'm looking for on my own.
There's usually more than one item in the area, which may be why it can show two peopel different directions to go to, I don't know. Blue/purple items are the kind that the seeker droid tends to notice and it keeps telling there is something until someone finds the special item in the area (which I have on multiple occasions).