Haplok

Not sure about melee, but ranged with dual mortars has a good chance.

The aoe from the Frostseeker is considered a separate attack and won't carry rogue affliction/DoT attacks. I'm also not sure if it will proc sneak attack bonuses. So mortars still win IMO.

Actually I did just that. Fighting Fonferrus' undead crew at level 15 was kinda rough, but I finally got the prize. The sword is very cool indeed, though it doesn't exactly outclass the other options (no accuracy bonus, less bonus speed/no extra attacks). Due to its lore and quests will now be one of my favorite crpg weapons, along with the likes of Dakkon's Zerth Blade and The Witcher's Aerondinght. I think the real advantage to rushing these quests is the opportunity to seize an awesome galleon-class ghost ship. What can be cooler? And with no monetary investment to boot. So a strong maritime presence at no cost = win.

For soloing that might be good. But I prefer 2 attack rolls from two hands for double affliction chance, +50% Sneak damage and + 50% speed from Streetfighter always on with a Blunderbuss (with possible +100% crit damage) and aoe option with dual mortar blunderbusses (rogue afflictions and DoTs also work in aoe!). Mortars target Reflex defence rather then the usual Deflection, so are typically very good vs slow meatshield enemies. For high reflex rogues switch to regular dual blunderbusses or pistols. The gun equipment is also better. Acina's Tricorn for extra speed and damage. Peter the Cat for +15% aoe damage and increased aoe size. Also you don't need both Crippling Strike and Confounding Blind for Deathblows. Blind is enough, as it also provides Flanked status = enough to trigger Deathblows. But don't worry about it, Deathblows is a level 19 ability for a multiclass, so game's mostly over by then. Streetfighter crazy bonuses with blunderbusses are active from level 1. The companion ability to get +10 Accuracy vs target the companion is attacking is called Stalker's Link. Unfortunately you first need to pick its pre-requisite, Protective Companion. Still worth it. I don't think a typical multiclass build can afford all 3 companion boosting abilities, unless you want to focus on the companion side. IMO just pick 1 of them at Power Level II, when you still have some spare ability points. I also skipped the Marked for the Hunt upgrade to Marked Prey and Evasive Fire upgrade to Evasive Roll - not enough spare abilities, base abilities are good enough IMO.

Except Blunderbuss Scout Streetfighters... those are OP but less fitting the archetype I guess.

You seem to be missing abilities at level 13 and 19.

It's not enough if enemies exceed you're engagement slots. They also must come from different angles. Not sure if different angles are enough if there is less of them then your slots. That said, recently I've had great difficulty getting my Swashbuckler to be flanked. Even when he's surrounded, enemies often don't cause "Flanked" or you temporarily gain and loose it. Of course, CC plays a role. But even without it, it's difficult to get and maintain the Flanked status.

Very possible and very easy. All rogue abilities work with ranged. There are one handed ranged weapons (pistols, blunderbusses) you can dual-wield for fast attack (and full attack ability spam). You can even do great aoe damage and aoe afflictions using the two aoe blunderbuss mortars from Serafen (the one he starts with and one you get in his quest). I think multiclasses tend to be a little stronger. I recommend Scout - Rogue/Ranger. Probably the strongest combination is Streetfighter/Sharpshooter. Streetfighter's mighty special is easily and constantly triggered on such a build using blunderbuss Powder Burns modal (distracts you and gives flanked status).

You don't even need expensive stuff like Captain's Banquet. Wael's Wind is pretty cheap I think. Reduction is enough, so also Luminous Lobster would work (or Svef drug).

It didn't work.. or did it work as advised - downgrading Dominate to Charm - which still turns your party members hostile? For Fampyr encounters, Immunity to Intellect is advised, not just resistance. And Shimmer Scale shield upgraded to protect from gazes and Blindness sources (Chillfog, Cipher Eyestrike, Curse of Blackened Sight).

Well, I would not say you gain 10 Int. You're not loosing 5 Int (but any item/food with Intellect resistance will ensure that also). And you could gain 5, but as I understand Frenzy Confused is canceled by Acute and both are removed? Unless you double-apply it, but then you burn double amount of resources on that. For martial classes I prefer 25% hit-to-crit conversion rather then a +1 PL bonus... As for stats, I don't know. I would dump Res to raise Perception and a little Con... but then again I don't play solo.

I think such effects only apply to their respective hand.

Hmm, Defiant Apparel hat? (Perception resistance)

Unbending is available at PL V, so earlierst level 13 for multiclass characters. Why Tactical Barrage? To fight Confusion? Better set a history that will spawn Devil of Caroc's Breastplate and use its enchantment. Or if dual wielding, use swords with Modwyr. It would be a shame to loose Disciplined Strikes Critical conversion. BotEP is not too shabby, but I think Eager Blade is a significantly better estoc. And yeah, you want more Perception for PotD.

Why Scepters? Without a melee weapon you miss on Carnage damage, no?

Also Devil of Caroc breastplate can be enchanted to provide Constitution Resistance.

Power Level VII though. Well, might be a cool combo on a pure Chanter, if one was inclined to roll one.

Whispers of the Endless paths is not optimal, IMO. The low base damage will hurt. And Carnage is only calculated once anyway - from the low damage. IMO go for Estocs (very high PEN, with Berserker/Devoted you'll frequently Overpenetrate for +30% damage and very good Estocs with aoe capabilities: Eager Blade available very early plus Engoliero de Espirs), alternatively with patch 2.1 go for 2handed battleaxes (new aoe battleaxe Amira can be bought early, eventually you may get Oathbreaker from BoW DLC) or Pollaxes - but you wrote you've done that already. Two damage types are not needed if you have high Penetration, IMO (particularly with Estocs). High defense against pierce means very little to an Estoc user, who will penetrate anyway (can reach up to 20 PEN with Hot Razor Skewers, you're always sitting on 18 with a Legendary weapon - enough for full penetration on Steel Golems). In practice few enemies are actually immune to a damage type and when you meet such foes, you can eat the penalty and switch. IMO having one damage type with high PEN is better then two low/medium PEN damage types. The difference is usually only 2-4 points of Armor and high base makes up for that.

Does it proc Blood Frenzy though? I thought Carnage couldn't crit?

Note that stats will vary depending on what multiclass you pick. If you choose Fighter or Chanter, I'd probably not dump Int, but try to have it high-ish.

There are quite many holes, already listed. But my vote goes for some cool morningstar.

Well, Brute IS a Fighter multiclass

I also advise against Helwalker. It will make you too squishy, particularly for solo. The Morningstar Brute builds are pretty cool. Morningstar modal lowers enemy Fortitude by 25 points, Staggered you apply with hits after Spirit Frenzy another 10 and they can make good use of that with Mule Kick and later passively with Brute Force. Eventually they can apply the debuffs in aoe with Clear Out. Here's one: https://forums.obsidian.net/topic/104272-class-build-william-will-breaker-12-solo-potd-brute/ Note I would not dump Constitution that much, particularly for solo and, like Boreorer pointed out in the comments, I'd definitely pick Mule Kick & Clear Out. One other solid Brute build that takes advantage of a very cool weapon is Cyrus' Stormbringer: https://forums.obsidian.net/topic/105374-roleplay-build-the-stormbringer-brute-off-tankaoe-nuker-for-potd-upscaled-updated/

Probably to go melee. Soulblade's Concentration on kill helps to avoid Interrupts up close and personal. And of course, Soul Annihilation provides a nice damage boost too. Can create a nice loop: Rogue ability attack builds Focus, SA spends it. Dumping Int solves the MAD issue of such a character. But the abysmal duration on stuff like Borrowed Instinct and Trickster defensive buffs, not to mention enemy debuffs/cc, would hurt too much for me.

Great suggestions, MaxQuest! Hope they might be implemented.