There's difficulty modes for a reason. Some people have a hard time with casual mode already, so even if it's too easy for you it doesn't mean other people will think the same.
Having a game that's nearly impossible to beat will scare off a lot of people from playing as it doesn't appeal to a wide audience, only a select few people who are really into the hard challenges the game would offer. Yes, some rebalancing may be in place at some point for the fight if it turns out to be too easy for a lot of people on multiple difficulties, but it also heavily depends on what mons you have on your team, so for now it's not going to happen unless it's proven that it's absolutely necessary.