EDIT: I was notified that Grape Bomb is not a Sharpshooter ability, I have no idea why I thought I read that in the ability tree. This severely weakens whatever argument I had, so proceed with caution if you do bother to read this, though I think it still stands as technically it's not for any class which makes it seem like a beneficial upgrade to everyone even though it hurts Sharpshooters.
I'm not sure if this has been posted before so apologies if this is a tired argument. If I'm just skill issuing really hard please let me know as well, but the ability for me is unusable.
Getting the Grape Bomb ability as a Sharpshooter is not beneficial in the slightest. If the following bombs after the first hit don't land on a target (which considering they are pretty hard to aim in a chain) they completely kill your stocked up Focus, which prevents you from using certain vital Sharpshooter abilities like Crepuscular Ray or Twain's Arc due to you losing all your Focus.
I'm not sure if Grape Bomb has the potential to be really useful in crowd situations where there are a lot of mobs and enemies for the bombs to bounce off of which can give Focus, never was able to try, but single enemy fights is just you throwing away whatever Focus you stocked up after using Arrow Bomb.
I think the easiest fix for this would be to prevent the following bombs after the first hit to not have any impact on Focus.
and
for obvious reasons