Voted for AS style, not because I prefer it over DS, but because I have a feeling that DS style combat would be extremely awkward and clumsy in Warcraft III engine.
I agree to that!
Is your intention PVE or PVP?
It is purely for PVE Campaign.
Ever played Devil may cry 4? That found a great balance between neo's Trickster(darksouls), and Dante's brawler.(Assassins creed) And from what i'm reading that is basically what you're after. could be that i'm missing your point of suggesting a roguelike approach to the ladder nightelves hide and walk tactics. (in that case you should look up The Mark of the ninja
I'll check them all, I can use any inspiration or creative techniques!
So how i would see it work in the warcraft engine. Every enemy minion hast a long cast animation wind-up. Much like Fel orc Warlock's Fireball Animation. with a fair amount of projectile distance. And the overall experience would be somewhat like the custom warcraft III Warlocks map
Warlock 1.01 - Warcraft 3 Maps - Epic War.com like offensive skill sets where you could pop a fireball mid air to make it scatter into AoE etc. But unlike the warlock maps has the knock-back based on missing % health to kick you into lava. Another map i'd suggest to take a look it is the Fufu ninja map.
Fufu United Ninja All-Stars 3.1 - Warcraft 3 Maps - Epic War.com With windwalk, shuriken toss, and dodge skill. It's as simple as a proof of concept to how i would see a trickster work.
Combo based attacks but when you get hit and as a result take damage the combocounter is reset. (selfbuff) Dodge(jump/roll/fly), block(shield, sword parry,) skills don't reset the combocounter but also don't at to it. And the unit deals 20+(X/X-1) damage on each attack.
The best part about my campaign would be being simple. We don't have to deal with spells because it will be based on reality. Ofc there will be fantasy stuff but more like AC4 assassins doing impossible things, not like warlock mage stuff. The campaign would be about Roman Gladiators, so I'll need close quarter fights a lot. I'll write an AI behaviour for combat based on the unit's skills as well. Some will mindlessly charge the player and will give many openings for attacks but keep the player constantly on their feet. and some enemies will just test the player for any openings forcing the players to attack more oftenly and wth different approaches. I'll even try to add some finishing moves for combats if I can, such as jumping from a wall and then doing some artistic stuff

As for what you have suggested, beginning enemies should have longer windup animations, so that the players can start calibrating to the style. But bosses or harder enemies should be faster and merciless. The system here would be a bit complicated which makes me scared a bit
Skillset:
Permanent Self buff: Fury (Combocounter).
It tracks the amount of hits you have done in succession when no instance of 5 damage or more is done on an enemy unit in the last 3s it starts losing counters automatically. 1charge per 4s. (would be the nicest to go back faster from 10 counter to 9 then it would take from 9 to 8. (but there's a formula possible here to make that happen) When your hero takes any instance of 5 damage or more it is reset to 1. Every counter increases Base damage by 5 damage.
Aura: Fear tactics:
Enemies in a 600 AoE from your hero. Are affected by a negative aura that start counting effective hits on them. Each unit that took damage in the last 2s get it's own counter the non affected units within 600 AoE can share the same counter up to that point. When a unit is no longer taking damage the debuff counter will lose 1 charge every 2nds. When the debuff counter gets back to 1 charge the unit is no longer negatively effected until he takes new damage. (easiest example would be -1armor per hit per counter per unit. )
This whole thing here is a great example, I didn't think of this combo counter in this way. More combo should mean something, and good thing is; you will be able to protect your combo from being broken by counterattacks(if AC style) or rolls/blocks(if DS style), or other hybrid stuff (if other style).
Magic Immunity 0.01 duration 1s cooldown
Hmm, so this'll remove any continuing spells on the player if any kills start happenning.
Armor up +9999 armor 0.01 duration 1s cooldown (tanks an physical dmg source blocking it from dealing any more damage than 1. )
Protects from damage during kills.
Enrage: add one additional Counter to Enrage 0.02 cast animation, 7s cooldown [i/]
Is this for a speed buff?
Ministun: 0.01 duration 1s Cooldown (interupt spells or attacks)
Good idea! I can use this for normal attacks as well. If our attacks could stagger the enemy unit, ministun him for faster detection.
leap/blink/windwalk 7s cooldown. (dodge projectiles)
Sword slash: Deals 3 x Base Damage (base damage is increased the Fury counters) And the -armor on enemies increase the raw damage received on the enemies end.
Cleave Attack: target in 350 AoE take 35% cleave damage
These can vary depending on map.
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Thanks a lot for your very detailed answer! I really appreciate it. I'll check your references and try to find a good mix of all combat styles. I don't want the campaign to be way too hard to grasp, or way too easy by spamming. There should be a middle ground!