Wasn't quite sure where to post this, but it does seem to be a bit of a bug. The AI does not counter influence well enough. I still have to try it on intelligent, but even at lower levels the AI needs to do a bit more work to counter influence.
I had no influence resources, just one influence starbase (right next to my own homeplanets, mostly to counter potential enemy influence), I did have the galactic wonders for influence, but no more than one Embassy (and it's followups) per planet.
I built up a strong military to stop the AI from attacking me, and then just let the influence do its thing. I eventually started gaining so many planets I couldn't even keep up with keeping them all properly built and defended. One turn I gained THREE new planets due to influence.
I love the influence part of the game, but it seems that every game I play, I can win through influence without even trying. An influence victory should be a dedicated effort to spread your influence, not just grabbing a few planets and building an embassy on each one, building two galactic wonders and voila, you've got 75% influence. But because the AI doesn't counter you, that does seem to be what happens.
I now play with the influence victory turned off, because it happens too quickly. By the time I finally get a neat empire going, the entire galaxy eats at my burger joints...
It shouldn't be that it becomes impossible to win through influence, but I think that if you want to get an influence victory, you should really have to work at it. Right now it just sorta happens.
Furthermore, the AI doesn't use his bonus tiles for influence. I've yet to see a planet where he actually builds an Embassy on a bonus influence tile. He typically has a factory or an orbital fleet manager on there. That's really just stupid...
Hope this helps somehow.
Creston