Oh I am finding them quite easy to defeat.
They show up in Grey Colored ships, baring a Skull for an emblem... maybe that's what they always look like but as I said this is my first experience with the game.
My Game Version according to Impulse is v1.32, dated 8/16/2011...
And correct, they are not arriving from the Phase Lanes... either that or these Phase Lanes must have a very Wide field of entry... if, looking at my Planet and its Gravity Well as though it were a Clock...
Then I have a Phase Lane at about 3 minutes past 3 O'clock, and one at around 9 O'Clock...
The Pirates are arriving at the point that would correspond with 1 O'Clock... According to my Map, they are based from a single planet, surrounded by the opposing Empire that I'm supposed to be defeated, but not doing very well at... as that one now has all planets except mine, and the Pirates. The Pirates Planet is situated so that they would have to pass through 4 other planets to reach mine, in a zip zag route along the phase lanes of those planets...
But instead, they're always coming at me from the 1 O'clock position, no where near any of my own phase lanes.
I'll see if I can get some replays of this occurring at some point as I do have the game saved and can load it up and have it happen...
Until then, I may start a new game on a new map with the pirates turned off!
I appreciate all the advise everyone here has given! 