What are your stats, background and fighting style?
Already you have a lot of conflicting or redundant features. If you have an idea of which one or two of your dozen or so features you absolutely want to focus on, this will make it easier to advise on which features to ignore since you can't possibly utilize all of them even if you had the stats to do so.
I absolutely want stunning strike, I absolutely want Zealous Presence, and I don't particularly need any feature from Vengance, but I need dem divine smites tho.
I was thinking 10 Barb, 6 Monk, 4 Pala. Also, I'm not 100% sure, but wouldn't the Holy Avenger Longsword be considered a monk weapon, since it can be used as a dex weapon?
Monk weapons are not based on whether or not they can use dex, and in any case, longswords can't use dex.
Monk weapons are shortswords and simple melee weapons that DO NOT have the two-handed or heavy property. Your full list of Monk weapons will be:
Shortsword, club, dagger, handaxe, javelin, light hammer, mace, quarterstaff, sickle, spear. You can "reskin" some of these, such as a club into nunchaku or sickle into a kama if you want more monk-themed weapons.
That is correct, the Holy Avenger Shortsword will work just fine.
A big problem you're going to have if you want to use a monk weapon is that the Great Weapon Fighting fighting style will only work with the Quarterstaff and Spear, and the second part of the Great Weapon Master feat doesn't apply to any monk weapon at all.
You can still use your ki abilities, such as Stunning Fist and Flurry of Blows, with any weapon.
War Caster may not be necessary since you seem mostly concerned about Divine Smite, and you can't cast or maintain spells while raging, but in case you do cast any spells, it's a good thing to have.
Sentinel might be your most important feat so you can keep enemies near you. Even with your increased speed, you want a target at the beginning of your turn in case you kill it and can move after.
So you'd recommend replacing GWM with Sentinel, and changing fighting styles? Cause, now that I'm taking the time to read everything, it seems like Duelist is the better option for her.
I'm never planning on using any spells from her. The spell slots are exclusively for Divine Smite.
I wasn't aware you had that option. Yes, I recommend replacing both GWF and GWM with Dueling and Sentinel. Using a two-handed/heavy weapon means your Martial Arts features are restricted, so no Monk damage die for increased damage (technically not an issue unless you were a level 11 Monk) and no Bonus Action attack. The Bonus Action attack wouldn't be so bad since you use it for Flurry of Blows, but that is only until you run out of ki points.
A Barbarian's Rage is less restrictive. It is only required that you use your Strength modifier for attack rolls when Raging and for Reckless Attack, and since your Strength is higher than your Dexterity you're fine there. It is natural to want to use a two-handed/heavy weapon for Barbarians, but by no means is it required.
I know it's not terribly well regarded, but if you swapped from Way the Open Palm to Kensei you could make a longsword one of your monk weapons. Not quite as dramatic as Open Palm though
I have a level 9 Goliath. 4 Vengeance, 3 Open Palm, 2 Barbarian (planning on Zealot)
What would be the best breakdown of level separation so that I can get the most out of all 3 classes? She will be taken to lvl 20.
Oh goodie! :D
What are your stats, background and fighting style?
Already you have a lot of conflicting or redundant features. If you have an idea of which one or two of your dozen or so features you absolutely want to focus on, this will make it easier to advise on which features to ignore since you can't possibly utilize all of them even if you had the stats to do so.
So I rolled for stats. Currently, this is her character sheet.
https://www.dndbeyond.com/profile/Megidramon5991/characters/15162508
I absolutely want stunning strike, I absolutely want Zealous Presence, and I don't particularly need any feature from Vengance, but I need dem divine smites tho.
I was thinking 10 Barb, 6 Monk, 4 Pala.
Also, I'm not 100% sure, but wouldn't the Holy Avenger Longsword be considered a monk weapon, since it can be used as a dex weapon?
Monk weapons are not based on whether or not they can use dex, and in any case, longswords can't use dex.
Monk weapons are shortswords and simple melee weapons that DO NOT have the two-handed or heavy property. Your full list of Monk weapons will be:
Shortsword, club, dagger, handaxe, javelin, light hammer, mace, quarterstaff, sickle, spear. You can "reskin" some of these, such as a club into nunchaku or sickle into a kama if you want more monk-themed weapons.
So, in order for me to use a Holy Avenger as a monk weapon, I'd have to use the Holy Avenger Shortsword?
Any rate, what would be the recommendation in terms of a couple feats for the character?
That is correct, the Holy Avenger Shortsword will work just fine.
A big problem you're going to have if you want to use a monk weapon is that the Great Weapon Fighting fighting style will only work with the Quarterstaff and Spear, and the second part of the Great Weapon Master feat doesn't apply to any monk weapon at all.
You can still use your ki abilities, such as Stunning Fist and Flurry of Blows, with any weapon.
War Caster may not be necessary since you seem mostly concerned about Divine Smite, and you can't cast or maintain spells while raging, but in case you do cast any spells, it's a good thing to have.
Sentinel might be your most important feat so you can keep enemies near you. Even with your increased speed, you want a target at the beginning of your turn in case you kill it and can move after.
So you'd recommend replacing GWM with Sentinel, and changing fighting styles? Cause, now that I'm taking the time to read everything, it seems like Duelist is the better option for her.
I'm never planning on using any spells from her. The spell slots are exclusively for Divine Smite.
I wasn't aware you had that option. Yes, I recommend replacing both GWF and GWM with Dueling and Sentinel. Using a two-handed/heavy weapon means your Martial Arts features are restricted, so no Monk damage die for increased damage (technically not an issue unless you were a level 11 Monk) and no Bonus Action attack. The Bonus Action attack wouldn't be so bad since you use it for Flurry of Blows, but that is only until you run out of ki points.
A Barbarian's Rage is less restrictive. It is only required that you use your Strength modifier for attack rolls when Raging and for Reckless Attack, and since your Strength is higher than your Dexterity you're fine there. It is natural to want to use a two-handed/heavy weapon for Barbarians, but by no means is it required.
I know it's not terribly well regarded, but if you swapped from Way the Open Palm to Kensei you could make a longsword one of your monk weapons. Not quite as dramatic as Open Palm though
I had considered it, but I want to stick with Open Palm, because it would make more sense for the build I'm going for.