Is Great War (or peace treaty in general) system fair?

To answer your one specific question: Vic2 didn't allow for any above-100 warscore outcomes, ever. This led to many events and decisions breaking the game's rules to preserve historical outcomes, with the most egregious example (and the weirdest, since it only did it halfway) being the U.S.'s western expansion.

To answer your more general question: yes, Great Wars are incredibly risky for more than just legitimate reasons. They're also risky because the AI is randomly terribad and you could wind up on the derp side of a dismantlement sandwich, even though you, in your comparatively-infinite player wisdom, could probably still squeeze out a win, or at least a white peace scenario (see below.) Just as you might get unlucky with your AI partners being terrible, you might also get unlucky with your specific wargoals - the ones targeting you, that is to say - getting enforced as part of a peace deal that you don't even get to negotiate in.

Do try to understand that with Great Wars specifically, the developers were trying to emulate the Treaty of Versailles outcome: a disastrous first foray into globalism that laid waste to an entire section of the "civilized" world and sowed the seeds for depression, revanchism and fascism. If the Great War mechanic hadn't somehow forced players to go all-in and all-for-one, then basic game theory - especially humans-against-dumb-AI game theory - would've made the whole thing a meaningless bit of fluff. You would've been able to pick apart the Great War alliances, wait out their exhaustion-accruing pushes, chokepoint them or naval-chokepoint them to death, and basically just play a race against the game's end date.

/r/paradoxplaza Thread