While I think that evacuation missions and CGs as a result of a Thargoid invasion would be good to have (or needed), I think that for such scenarios there needs a serious escalation of the Thargoid situation before evacuations are required.
Evacuating systems is the last resort.
What would be nice is a slowly* changing public perception of the Thargoid situation with more and more people willing to get a way from the Pleiades (refugee missions that don't negatively affect the BGS of the accepting faction) and GalNet stories about that development.
In addition we could get news of stations going "dark" - first small ones, than bigger ones - then we could witness those attacks and things turning really bad.
At that point superpower organized evacuations would begin.
Short: it's too early for evacuations
Edit: Pacing of a story is important in my opinion. A MMO has the problem that a global story always moves too slow or too fast, depending on how much a player plays the game.
If the story moves to fast people will adapt to the new situation and it will get boring quickly.
Imagine a full scale invasion from day one - that would have been a few weeks now - and there is only so much to do. A slower story progression allows more uncertainty, more suspense and yes more spreading out of the content over time until the next thing is ready that will distract players
