Just a patch before people complained pirates are too hard, and now you want to buff them again? Pirates should be nuisance on normal difficulty, not a major force to reckon with.

Okay for the difficulty, guys, but maybe normal could be upped a little bit (or be renamed to easy) because it felt really underwhelming.

As for my other points, I was only playing with serious AIs, so they shouldn't have that much bonus Dust, but even I could afford to buy back marks all the time without even focusing on Dust. I'm on turn 120, Dust inflation is almost 3x yet the mark's cost to buy back is still 1800, which is almost what I produce each turn...

I agree with the OP's statements. 

I bought a few pirate marks in my previous game and on the next turn from buying those marks they returned with an empty report saying: "The contract was bought out".

It would be really handy to determine the price of the contract yourself.

Had similar experiences to Sublustris and Plutar. Pirates on Endless difficulty are terrifying, and there is a proxy economy war going on throughout the game just to keep them off your back and bothering others. Makes early dust production pretty important, and I was actively selling my resources a lot more just to keep them away from my Arks. I hadn't clocked how much Vaulters really have the edge when it comes to pirates. So maybe ramp up the pirate difficulty a bit more. The AI will handle it on hard. 

As for the suggestions you made, I would put that in the Ideas section (I did one on pirates a while back) since the DEV's will be more likely to see it and maybe implement it

Kuma wrote:

I wouldn't want the AIs to struggle against them, either, but I was planning on giving it another go later. It doesn't fix the other issues I mentionned though, does it?

I agree with Plutar, Endless pirates drastically change the game and provide a good challenge

As for the AI, the pirates shouldn't pose too much of a challenge as long as the AI is also on Endless or some other high level difficulty 

Try endless on the pirates. Normal Pirates are very easy like a gentle pile of experience for Your Heroes to gobble up. Trust me when I say endless Pirates are endless. I'm posting this from my phone however I have shared a screen capture that shows over 70 pirate ships on a given mark. There difficulty changes quite drastically from setting to setting.