From what I've seen, unless a friendly is dragging you to them, wirbles are pretty damn aggressive, especially when in groups. On occasion I've seen them make serious attempts to shoot me down at 5k, but 3k (1k icon range for them) seems to pretty reliably stir them up.
Not perfectly reliable, but its the balance I've personally found as acceptable.
Besides, the goal is not to spot them or their icons, but to make them open fire. Unless the guy shooting at you is either incredibly skilled or uncommonly lucky, you'll exit their effective range before they get too close (it takes only 7.6 seconds at 300mph), and you know roughly where he is.