Well there is also a game breaking bug that is probably the reason that you wont find many Neon Arrow or Phantom weapon mods in the vanilla game. If you spawn more of them with console commands, you'll soon learn that both of these mods, when applied to a weapon, have broken math applied to the damage and DPS. For example, I craft a brand new Iconic "Problem Solver" (the crafting spec says it's damage should be 106-130 at Legendary quality). When I look at the new weapon in my inventory the damage is actually only 51-62 and it's DPS is 909.2. Now I apply 4x Phantom mods to it (+5% firing rate increase, for a total of +20% rate increase). While the weapon physically seems to actually fire bullets faster, the DPS will still say the same number as it did before putting those mods onto it (909.2) despite the fact that the Attacks Per Seconds is now 20.02 (which is insanely fast, btw). How can the DPS not go up?!? But.... Furthermore, the weapons actual damage rating goes down. With the mods installed the damage goes down to 40-49.
Now, there is actually a mod on Nexus that aims to fix this particular issue, but I don't know what side effects this mod could possibly be causing as far as things like Damage Buff Perks. None of the following flat damage buffs seem to apply any provable damage increase. Hail of Bullets, BulletJock, or Desperado. When those perks are purchased, there's no physical way to prove that they do anything or not. The weapon's description card wont change, and if you attempt to make a save and do Pre-perk/post-perk tests, that will prove nothing because each shot that hits the target will say wildly different numbers due to things like +28-35 Physical Damage, or +Chemical/shock damage... Many people have been saying these perks have been non-functional for several game patches.
My thoughts are that since it's not really possible to prove that the do or don't work, people by and large just buy the perks and assume they work fine and CDPR is probably okay with that. And now that we've got the official announcement that the game will only get 1 expansion and they already announced cyberpunk's sequal... It's not looking good that these things will ever get fixed unless modders do it.