They do not need them. The build I use focuses around the maggie and celestial lawbringer and uses 7 out of 11 skills from FTH (well over half). It’s the faster fire rate skills that are useless to Jakobs. That said, Jakobs pistols fire fast enough (just let go of the right stick and slap that right trigger, or click faster). As other have pointed out there are plenty of other weapons that do make great use of it.
I don’t get why this tree should be wholly dedicated to all pistols, which seems to be what you’re making a case for (maybe i’m misreading that). The name is Fan the Hammer: you can only fan the hammer on a revolver, and there’s only one manufacturer making revolvers: Jakobs. Wikipedia about fanning: “Fanning is a revolver shooting technique in which one hand holds the trigger and the other hits the hammer repeatedly.”
So I wouldn’t call the entire tree broken, far from it. It’s just that the faster fire rate bonuses do not make sense since Jakobs weapons fire as fast as you can pull the trigger. Also since fanning the hammer using both hands, one for each of ya does not make sense in this tree. So I agree that the tree is a bit of a mess in terms of skills, but it’s not broken.
(which would make a lot more sense from a design perspective)

