@Mrfuji to be honnest I cannot imagine how it could be possible to translate the facing rules in BG3. It means an AC that is different in front and on our side if we have a shield. It means being able to rotate our characters as a proper reaction which could eventually be possible but possible exploitable.
Not sure how it works with multi attack in the PnP, maybe you'll be able to enlighten me.
I'm moving behind and use my first attack. Ennemy react and face my character. I'm moving behind once again because I still have movement and use my second attack with advantage. Imo this would quickly become boring. How to prevent this ?
About the feats I really don't know. If my dexterity is 11/13/15/17 I'll have all the bonuses in your point 1) too, which as you said may be very OP.
About damages yes. Definitely. The more I think about it, the more I think it could be a very cool homebrew.
The problem with Facing is exactly as you said, because in 5e you can freely circle around enemies. My ruling would be: when you move from someone's front or side arcs to their back, they get an AoO because you're leaving their threatened area (their front and sides). This is maybe a valid interpretation of the rules, depending on how you read the lines "A creature can normally only target areas in their front and side arcs [for Facing]" and "You can make an opportunity Attack when a Hostile creature that you can see moves out of your reach." Thus, you're trading getting AoO'd for advantage on your attack(s).
Proficiency Bonus to damage is consistent with many feats & class abilities. It's possibly slightly too powerful but eh whatever.
Originally Posted by DragonSnooz
I think a feat that gives the player easy advantage on attack rolls would become an auto-pick. War Caster with advantage on con saving throws is a really strong pick. Maybe a +2 to hit from high ground to replace sharp shooter and a +2 to hit from backstab as feats.
Quite possibly my suggestions are too powerful. However, alone (and separate?) you suggestions seem too weak. You already get a +1 from just increasing the relevant stat, plus other bonuses. Maybe if you got +1 to Dex and +2 to hit from high ground, and the ~same for the backstab feats?