Dude, what? Overusing Trin's power resulting in a fairly minor downside is not remotely arbitrary, the game is constantly telling you how immoral her magic is. You murdered a teenager for being a spoiled brat and so you could gain a minor benefit from replacing her. That you're shocked this had negative consequences in a game whose protagonist's goal, all along, has been to make his world a better place is entirely on you.
Also if you're that angry about the idea of replaying part of this game to get a better outcome this probably isn't a game for you. Sierra's constantly adding flags to record minor-seeming actions. Some are red herrings to throw off the hardcore fans, some have immediate effects, and some have consequences a year or more later (both in and out of game). The "optimal" path gets rewritten with almost every update, sometimes going back over a Chapter because of how intricate all the interactions are between the game's choices.
I made the exact same dumb (in hindsight) decision you did, expecting minor downsides down the road to make up for its minor upside. When said minor downsides turned out to be different than I expected, and slightly more extreme, my reaction wasn't "Ugh, now I have to go replay the Erosian War", it was "Huh, a reason to go replay the Erosian War. Might as well back up a little further and replay the Tower Depths as well, I always love that section." If replaying part of this game because new-but-predictable consequences got added makes you mad, you should consider waiting to play it until development's finished.