Kaylon

Monk/soul blade can have very high defenses while dealing also incredible damage. Sun and Moon + Tuotilo's Palm + Left Hand of the Obscured coupled with high accuracy (Borrowed Instinct) and Swift Flurry/Heartbeat Drumming are devastating with Soul Annihilation. The double hits of Sun and Moon will trigger Swift Flurry/Heartbeat Drumming even multiple times in a row recharging your focus after each Soul Annihilation. You will also terrify your target causing often disengagement attacks for even more free hits.

Ghost heart/ascendant with Frostseeker is a very fun/versatile ranged build with solid ranged damage and casting abilities. However if you want to play just a caster then the potential of Frostseeker is a bit wasted...

Ascendant/helwalker is the best combo for a caster cipher. Chromoprismatic Staff with Instruments of Pain is the most efficient way to recharge your focus because you can benefit from Swift Flurry/Heartbeat Drumming/Turning Wheel while attacking from range.

A trickster/soulblade can gain focus pretty fast and you can stack multiple dots on enemies.

Priest/streetfighter combo has good synergies and the 30% lash on spiritual weapons is pretty good. Druid/Trickster using Firebrand can work too.

Maybe I was thinking about Frenzy and Swift Strikes and I assumed that Tactical Barrage is suppressed by Frenzy too. However they should stack indeed because the hit to crit from Frenzy applies only to melee weapons, while the one from Disciplined Strikes works with all attacks.

You can't do the same with Set to Their Purpose... ?

If I remember well it appears as suppressed in the active affects when you put your mouse over character's portrait during combat. I never really tested because it made sense to me...

Disciplined Strikes will be suppressed by Berserker Frenzy thus you should pick Tactical Barrage instead. With Barbaric Blow you will have 1-(1-0.3)*(1-0.3)=51% hit to crit chance. Here's the link @Not So Clever Hound mentioned earlier

Powder Burns distracts, doesn't confuse. A streetfighter/troubadour might be a better combo because Chillfogs benefit from sneak attack, deathblows and heating up bonuses.

Streetfighter gets bonuses while bloodied or/and flanked. If bloodied you will get 50% dmg bonus and 50% recovery reduction. If also flanked (not hard if you're attacked by 2-3 enemies) you get also 100% crit dmg bonus. Rogues gain also immunity to mind afflictions while bloodied and Shark Soup gives immunity to body afflictions. Wael adds some defensive spells which aren't very useful for you. The subclasses I would consider are Berath, Magran or Woedica (if you don't mind being cruel) - those have useful offensive spells and good spiritual weapons. For end game items look for High Harbinger's Robes, Claim and Refusal, Horns of the Aurochs, Hylea's Talons, Belt of Magran's Chosen, Fjord, Voidwheel...

If you don't solo then any class is viable. RES/CON make little difference in the early game and once you have BDD/SoT they become irrelevant - the ideal would be max PER/INT/DEX and rest in MIG. I prefer human race since the bonuses apply to all attacks, while also wearing a helmet. However +3PL can give more PEN/projectiles to spells which might be more important for pure casters.

The herald can certainly solo everything . He doesn't require any cheap tactics or exploits, however he's not a fast killer and some people find this style of play boring. The arcane knight (blood mage/paladin) is another great solo character with more offensive power than the herald while just as sturdy - but requires more micro. SC forbidden fist is also great and very fun once you can spam WotW. If you like to be a sniper then assassin/tactician is another great solo character. All above characters are very effective from the beginning to the end. Priest/x requires BDD/SoT to be strong (without that it becomes just an average class) and is micro intensive. Blood mage, streetfighter, ascendant, bellower, helwalker are all good combos for the priest.

All of them work with any party composition in PoE1/PoE2. However in PoE2 multiclassing them gives better results.

Stoic Steel is very good. You should choose Swift Flurry at creation, skip Force of Anguish and pick Righteous Soul later. Also you should drop Improved Critical and pick Lesser Wounds instead.

Stats are ok. Personally I would go with lower resolve and higher int/per. For a melee monk Enduring Dance isn't worth investing because it won't last very long and doesn't stack with Exalted Focus. I would pick also Enervating Blows in order to keep my target afflicted and be able to drain health. Uncanny Luck is pretty worthless, it's better to pick Tough to compensate the low Con. Rooting Pain is free AoE damage and since you will generate wounds like crazy you should also pick it. Inspired Defenses doesn't help if you aren't a tank. Scion of Flame is good only if you pick Sacred Immolation and Brand Enemy (which are by the way very good choices for a monk/paladin since the monk can remove the self damage from Sacred Immolation using Clarity of Agony).

Steel Garrote/Assassin is a good sniper and has very good survivability because he can drain health with each hit on top of his infinite regeneration. The Tactician/Assassin can recover his resources and can also be played as a sniper/melee.

Steel Garrote/Nalpazca (or Helwalker) using Voidwheel is a great combo (AoE damage dealer/CC) because he can spam Torment's Reach/Raised Torment at leisure.

Without these abilities you can't solo unless you plan to do a mostly pacifist run and skip the hard encounters... If you really are serious about soloing without exploits and play as a melee wizard then you should try steel garrote / blood mage.

I found another speed buff (it stacks with Tempered Fury and Bolting Strikes) - Spirit Siphon (15% action speed) from Less/Least Unstable Coil.

It took when I tried to beat it with the herald... With the assassin I gave up pretty fast because I tried mostly to prevent the split since the phase 2 seemed impossible without hard CCs. I remember I tried interrupts also, however I didn't try Overbearing Shot because I thought it was too slow. Lately I was thinking what would be the best weapon to interrupt the merge if I had Blade Cascade. Once I figured I can shoot fast enough even without Blade Cascade it went pretty fast.

Another must have buff is Bolting Strikes (15%spd & shock) from Lord Darryn's Voulge. There's also Highwayman (20acc with ranged weapons) from Scordeo's Edge (stacks with Adaptive). I confirm that Attuned Channel from Weyc's Wand works and is great. Empowered Being (all lvl3 inspirations) from Least Unstable Coil works great, however if you're hit by afflictions your inspirations will degrade if you're not immune (that's the case for all inspirations buffs).

I finally found a reliable way to beat Hauani-O-Whe. ✌️ The missing part of the puzzle was the unique arbalest Mechanical Marvel which attacks in a line (max 3 targets) and can be enchanted with 25% recovery reduction. With Acina's Tricorn, Sharpshooter's Garb, Abraham/Cutthroat Cosmo and Captain's Banquet it's possible to shoot every 4.1s with Overbearing Shot activated. Overbearing Shot knocks the oozes prone interrupting them and gives you enough time to shoot them again before they're able to merge. How it works: Step1: Kill the first form (like in the video) Step2: Use the arbalest to remove the concentration from both gigantic oozes then shoot one of them until it's close to 50%hp. After that you can apply Arterial Strike/Gouging Strike and wait until it becomes Bloodied - now as soon as the oozes see each other they will try to merge. The only tricky part is to position yourself in line with both of them (not that hard once you understand the timing). Once the oozes are close to each other they will try to merge over and over again and you'll interrupt them over and over with your arbalest until the one with lesser health dies. Step3: We have now one gigantic and 2 massive oozes. The massive oozes don't patrol and it's a good idea to kill the gigantic one near the left/right sides of the area. The other gigantic ooze will continue to patrol and should be killed on the opposite side of the area. Step4: We have now 2 pairs of massive oozes which are far from each other. Killing the first pair works the same way as for the gigantic - remove their concentration, shoot one of them until close to 75% and when they start to merge interrupt them over and over until one of them dies. Step5: One massive ooze will split in 2 greater ones while the other massive one is near death. Now it's time for the scrolls: the greater ones are killed with 2 Tornados (it also knocks them up which interrupts them), while the 4 lesser ones are killed with a single Tornado. Step6: Kill the second massive ooze and destroy the greater/lesser ones with another 3 Tornados. Step7: Repeat steps 4-6 for the other pair of massive oozes. Observations: The scrolls of Tornado don't require very rare ingredients and only 12 scrolls are needed. That means we can have 3 quick slots free for other consumables (potions of Ascension, drugs, potions, etc) Maybe it's possible to reach the required speed with just Coral Snuff instead of Captain's Banquet (which is less useful for the other encounters).

You can also apply a long confuse to yourself using Fugue Spores poison, however you need items with health regen to sustain the dot damage.

Didn't manage to replicate your trick. Maybe it was a bug...