We've done a lot of playthroughs on this map with between 20 and 40 players on b15s, and we have some consistent points of friction.
Firstly, one of the neat things, I think, about the map is that Blue doesn't generally have
great forward sentry spots, and Red generally has a lot of flanking potential. The stages also generally have long-ish walks to the final point. This puts an emphasis on good, active Engineering on Blue which is a nice change of pace.
However, this aspect is overall frustrating on stage 3, final point. There's just not a good way to secure Blue's left flank, between the multiple routes available to Red, Demo's indirect fire capabilities, and the closeness of Red's spawn. Combined with the long-ish walk from Blue spawn and the outward pressure from the defense of the point itself, Blue is often being sandwiched before or even during an attack with what feels like no good way to answer it.
Secondly, stage two, final point has been where most offenses end. Even particularly good offenses stall on the last few feet, for whatever reason. One problem is that it is critical that Blue takes advantage of the underwater flank, but even after a lot of time spent on this exact point, most players do not know it exists. I think it would be an improvement to make this path much more obvious to Blue, even if it's just slapping a giant arrow over the tunnel helping people know it exists.
Additionally, because the capture area is so narrow, and because the cart is excellent cover for both teams, it really is difficult to get those final few feet in. It's generally more frustrating than fun to dislodge a RED person nestled in between the cart and the cover of the "cart elevator". I feel like at a certain point if both teams are touching the cart it's hard to actually get around the cart and into that space? Making it a bit wider, even asymmetrically on the Blue side, might be nice. The key takeaway I have is that whenever the cart starts helping RED more than BLUE, it is a uniquely frustrating feeling.