No. And while, the aforementioned difficulty thing is true, its actual effect greatly varies depending on scenario since the enemy AI is better too.
It is certainly the most fun at Hard though, at least from my point of view. If it is harder than a higher or lower setting is hard to say.
Standoff is a difficult game, at least compared to most other WC games. As with many fan games, balancing is made by people who play the game a lot and, in contrast to a professional production, no external testing groups with fewer experience exist to "reign it in". If that is a good or bad thing is a matter of perspective.
Personally, I think the assault on the pirate asteroid base during the prologue is actually the hardest part of the entire game, at least if you want the mission to go perfectly. Hence, if you get stuck there, you might want to skip ahead of the main campaign.