How many two-skill +2/+4 bonus feats are there and is it balanced to homebrew more?

Question

Each skill except for Appraise, Linguistics, Craft, Perform, and Profession corresponds to a core feat that has no prerequisites and grants +2 to two skills or +4 if you have 10 or more ranks. Those feats are:

• Acrobatic: Acrobatics and Fly
• Alertness: Perception and Sense Motive
• Animal Affinity: Handle Animal and Ride
• Athletic: Climb and Swim
• Deceitful: Bluff and Disguise
• Deft Hands: Disable Device and Sleight of Hand
• Magical Aptitude: Spellcraft and Use Magic Device
• Persuasive: Diplomacy and Intimidate
• Self-Sufficient: Heal and Survival
• Stealthy: Escape Artist and Stealth

There's also Prodigy, which lets you pick from two different Craft, Perform, or Profession skills.

Beyond this standard list, there are a few feats that have a similar effect and either stack on top of the same skills (such as Uncanny Alertness, which grants bonuses to Perception and Sense Motive like Alertness) or apply to a skill pair that is not covered by an existing feat (such as Oracular Intuition, which grants bonuses to Sense Motive and Spellcraft). Voice of the Sibyl is kind of similar, although it doesn't quite fit into the same pattern.

What other feats follow this +2/+4 to two skills format? I'm looking for Bluff/Diplomacy in particular because I'm considering creating a feat for that pair. I'm concerned that it may be too powerful since it can be taken in conjunction with Deceitful and/or Persuasive as an easy way to pump those skills. Is this actually efficient enough that such a feat would be overpowered? What about other overlapping feats such as Stealth/Bluff or Perception/Survival?

Answer 1

Google returns 37 results for site:https://aonprd.com/FeatDisplay.aspx "If you have 10 or more ranks in one of these skills, the bonus increases to +4 for that skill.", which should cover each of these feats. There are false positives, however, so there are not 37 of these feats. Sifting through the results, I leave as an exercise to the reader.

As for the second question, no, it is not balanced to homebrew more—these feats are 100% traps that should absolutely never be taken.¹ Adding more only gives players more opportunities to make the mistake of taking them. Bluff and Diplomacy are two of the most powerful skills in the game, and pumping those, Diplomacy in particular, can easily break the game if those are run as-written (which almost no one does), but either you’re breaking the game with a too-high bonus, which isn’t good for the game, or you’re wasting a feat on a small incremental boost to something you were already good at, which isn’t good for the game either.

These feats are bad. Don’t take them, and don’t add more of them.²

1. _{I will add one caveat—if something truly great requires one of these feats, that might be a reason to take them. But since that thing now costs an extra feat on top of whatever it would usually cost, that’s a real stiff price and not many things are going to be worth it. Nothing immediately comes to mind that would qualify for this caveat, though I haven’t thought about it too hard.}

2. _{For what it’s worth, I’m the author of highly-acclaimed third-party Pathfinder content. It’s extremely difficult to really provide the proper context for the strong condemnation I have for these feats, but at least know that I am coming from a place of expertise. Also, this is not a condemnation of anyone who read these feats and thought they were good. That isn’t any reader’s fault—it’s Wizards of the Coast’s, for writing them in the first place, and Paizo’s, for not fixing them (enough) when porting them to Pathfinder. The books are written as if these were equally-good options that you should consider if you are interested in these skills, so it is entirely reasonable for readers to expect that to be true. The books are just simply wrong about that, which is awful.}