Just chiming in to generally agree. Boundary Beyond is a hard scenario (I wouldn't call it "imbalanced", but that's such a matter of opinion I also wouldn't argue about it). And, even though it's hard in general, there are definitely some team compositions that will struggle more than others.

Also, just to check you know: the game is designed so that you (usually) just move on to the next scenario whether you "pass" or not. Failing BB and then moving on to the next scenario is fine* (edit below), and you can still win the overall campaign. I almost never replay scenarios, even if our group fails one way or another.

There are just a few scenarios in the whole franchise where investigators will be killed or driven insane instead of just defeated. (You may have already encountered one of those, or you might not have noticed!) Sometimes the second-to-last scenario in a campaign will tell you that you lose the campaign if you lose that scenario. Usually though, you just move on, a little worse for wear, but still trudging ahead. It's one of the things that I find unique about ahlcg. I've been playing for some years now, and I appreciate that the game can still beat me up a little.

*EDIT: what I mean is, moving on is actually intended game play according to the rules; it's also "fine", in a broader sense, to adjust the game in absolutely any way that makes it fun!