by GregDarcy
I agree with the general consensus. No you don't NEED any expansions.However, the promo encounters (not the encounters expansion) add extra replayability without otherwise changing the game. I cannot comment on the expansion encounters as I don't have them yet, but they were fan designed and seem to be somewhat unbalanced and situational.
Invaders is great. The two new faction play very differently to the others and take a while to learn how to get the best out of them. Until you do, they will seem underpowered. Once you get your head around them, they are at least as powerful as any of the others. We often use one or both even in 2p games.
I haven't played much with wind gambit or Fenris. All I can say about them is they don't really seem necessary.
I do really like the realistic resources and the encounter campfires, but they are by no means necessary. The encounter campfires are probably closer to necessary, but while I have played with them, I don't own them (yet!)