I agree with a lot of this. While most of what I'm going to say is in my P6 LP, worth writing down where I agree and don't because I think this is a really solid base to start from. Boulder stance: agree, it's one of the strongest cards and could stand to be toned down. Maybe make the decision Pale vs. Ambush or something, instead of 1 vs 2.
Not sure which card you're referring to with "Bolster", so ignoring that one.
For official papers, I think the biggest mark against it is that Negotiation is so easy you would always prefer a Battle faction card than a Negotiation one - I think that they should probably just all be made battle cards, tbh. But yes, even among special negotiations this is a stinker.
Scatter - maybe this is also experimental, don't recognize it either.
Feint - I think Feint has some pretty powerful upgrades (the heal and cleanse ones) that I want to keep until the end. I do think with the Fatigue change it's probably worth re-evaluating whether the xp cost can do down.
Totally agree re: Alleviate.
Agree that Calm is strong relative to other composure sources, but composure in general isn't the strongest thing so I don't think that's so bad. It does seem reasonably thematic that Diplomacy gets inherently better Composure options than Hostility.
Agree that Cynotrainer seems bad even in Discard decks. One or the other should be non-random on the base card.
Agree Obtuse/Attitude being identical is weird.
Agree Gouge is nigh-superfluous. Would be interesting to make it a weak piercing attack instead, so you had something for robots.
re: Barnacles, I think it's maybe a little better to get the action but scaling is not to be underestimated for long fights, esp. with multi-hitting enemies. Though it could probably stand to be a +2 bleed increase instead.
Disagree on 2's being inherently kinda bad. Looking through my unlocks - Cross is fine, Barnacle is strong, Muscle Memory is situational but good with some decks, whatever that one card is called that applies bleed then does bleed based damage. You probably need an energy boss relic if you have more than 1 or 2 of them, but that's no big indictment imo.
I agree with almost everything in your "other" section. I will say the Bartender is not so much "it's borderline impossible to beat without a specific way" - I think both hostility and diplomacy have pretty much "one true deck" at present that only uses 1-2 manipulation cards beyond the starting ones, so my decks are usually bartender safe - as much as "the existence of Bartender makes a lot of purple cards unplayable, and means I will virtually never experimental with manipulation based combos as the core of my deck". So it's still really bad because it limits a huge variety of stuff, but I think the bog-standard "just pick the good cards in your color" decks do fine into it. Just a shame that there's such a powerful incentive to never try anything new.