When I refer to WoW Classic I am specifically referring to vanilla 1-60 WoW. I am just covering my opinion on why wow exploded in popularity and what contributes to a good mmo class design. There are a lot of things ashes is nailing right on the head, better than wow would have ever dreamed of such as the node systems, node wars, caravans, and all the player interaction in between. WoW had very fluid good feeling combat, something that ashes is also on track to have as well.
Vanilla WoW is a game that pulls many of us back on and off for years and years. The leveling in that game is so basic yet addicting. Every class was distinct and represented its fantasy perfectly.
The specializations of each class in wow were also well made. First of all you got one point every level to look forward to. You could multi specialize between three different talent trees, you had so many choices to make to custom tune your character exactly how you wanted them to be.
I have some concerns about the flavor or fantasy of the classes in AoC so I figured now that the classes are beginning to be fleshed out i'd voice some of that here. For example, having a class named tank, could severely limit the possibilities of other classes tanking. In classic wow warriors, druids, paladins, and shamans could all tank dungeons, for raids it was typically druids and warriors, perhaps paladins but I never really played alliance to find out. Also many classes could fill different roles and specialize in many different ways, they all had something unique they brought to the table. Whether it was buffs, mage food/water, warlock healthstones, shaman totems, paladin aura's, warrior shouts, and on and on. There were many hybrid like classes with the shaman druid and paladin which were very versatile. The combined primary and secondary class names give people a lot of hope for the fantasy of the class, although some of the summoner ones do look very interesting as it changes their summons other than that it seems to be mostly merely a name.
Warrior- Warriors had their own unique rage system, that came with a mini game of balancing stances with their own abilities and advantages and disadvantages with each stance, a good warrior was a master at managing his rage when switching stances. They also knew that sometimes it was necessary mid battle to switch to the sword and board to absorb damage or bash a spell, then switch back to dish it out. When a warrior changes stances he lost all his rage unless he specialized to keep around 20 when changing, this mini game was addictive. They never used any magic, all their attacks and abilities were based around their weapon and rage as well as their tankyness and aggressive rageful demeanor. They had distinct specializations that encouraged tanking and becoming a stun menace or dual wielding and 2 handed weapons. Which you could blend to make your own custom built character, taking aspects from all, or two. Warriors were fierce their fantasy was well done between the rage system, shouts to buff yourself and allies, stances lack of magics or anything appearing magical, and more. Warriors are my favorite so im a bit biased. The idea of a warrior with mana makes me queasy, same for a warrior with magical looking attacks. It just doesnt seem to fit the fantasy at all.
Mage- Mage's were very interesting, They specialized in arcane and elemental magic. For their go to basic spell attack there was three versions, arcane missles, fireball, they all had slight differences, the arcane missles were channeled and went around walls, frostbolt slowed targets, fireball did the most damage and left a small burn over time. You could specialize for each of these types, or mix match your specialization. It greatly mattered to recognize what type of mage you were battling to know how to fight them best. Every specialization felt like its own class. If you played wow PvP you know how fierce the arcane fire multi specialized mages were. Or if you were a warrior like me, how annoying the frost mages can be. Mages could open portals across the world, create food and water for friends. They could buff allies with extra intellect, remove curses from allies. They sported big damage especially in AOE, This added to the mage fantasy and really made it a interesting powerful but squishy ally to have around.
Warlock- Many time's multiple spell casters in games can feel to similar, this was not the case with the warlock. The warlock had life drains, mana drains, summoned evil looking pets, curses, fears. You could specialize for damage over time and drains, or big burst nukes, or specialize for your pets and be way tankier than the other specializations. It's not often you see a tanky caster. They could harvest souls of conquered foes to summon stronger pets. They could also use souls to create healthstones that act as health potions for allies, or soulstones to revive the fallen if it was used prior to their death. They had their own special dreadsteed mount which was epic. The Warlock fantasy is truely near perfect and I dont even play warlocks.
Druid- A true hybrid class, they sported damaging spells, healing, and shape shifts for physical damage and utility/stuns. The specializations were for each of those three things. However even a spellcasting or healing druid would shape shift for either the cat forms stealth, or bears stun, and on and on. Bear had rage instead of mana like the warrior, cat had energy instead of mana like the rogue As would the feral shapeshifting specialization use heals and damaging spells. They had innervate which would replenish mana of a ally swiftly, a couple buffs, as well as great healing over time. The jack of all trades. The nature aspect of this class was excellently implemented. This class could tank dungeons and raids. This was the only class who could resurect a ally in the middle of a battle.
Shaman- Another true hybrid class, they didn't use shapeshifts they used the power of the elements to buff their weapons, and cast their spells. They had totems that buffed themselves and their team, or the fire totems could dish out damage, one for each element could be deployed at a time. The buffs ranged from melee, to mana, healing, fear and sleep removal, strength, agility, tankyness. They were a necessity in raids for these buffs. They had a chain heal, one of few heal spells that targeted multiple allies. Some of my fondest memories were playing a hybrid specialized shaman dealing massive spell damage and weapon attack damage with my two handed weapon buffed with the element of air. This class could even tank dungeons, however not raids. The elements and totems really gave this class a unique fantasy. Each quest for your new element totem was epic.
Paladin- The paladin used the holy light to heal allies and damage foes. They could be seen sporting a big two handed weapon or a sword and board. This class had auras that would buff themselves and allies with armor, or reduced knockback on spells, resistances against damage types and more. They had a unique system of judgements and seals, they would cast a seal that would buff their attacks in various ways, then they could expend it on their opponent in a judgement for additional damage or a debuff on them, for example everytime they are hit it returns mana to the attacker or, holy damage vulnerabilities to add to your future attacks. They also had their own special mount which was cool. This class was versatile, able to tank, heal, or damage. The class fantasy although cliche, was very well done.
Priest- Priests could be nasty nasty damage dealers, or healers and buffers. It was always good to make friends with a priest. If they specialized shadow they had shadow form which was iconic and really bad ass looking. Increasing their shadow damage while in it but also not allowing them to cast holy spells. They had one of the best buffs in the game increasing max health of your allies. They had shields, a heal over time, they could negative remove magical effects from allies, even holy priests could dish out some serious damage if you knew what you were doing. Discipline specialized priests could massively buff allies or themself with a huge spell damage buff.
Rogues- Rogues had a very cool take on what they do, they had stealth so they could creep around invisibly. They had energy instead of rage or mana. Special moves that require stealth that gave them potent openers in combat. Poisons to apply to their weapons which had various effects of slows, instant damage, damage over time, reduction in healing received. They had combo points which they would stack up from their basic abilities up to 5 combo points, to use a finisher move that would either stun, nuke, or bleed their opponent over time. Their specializations focused on either the combo points and finishers, or they could play like a swashbuckler with dual wield swords and parry riposte, or they could play as a huge burst initiator from stealth. Or as with all classes in WoW they could hybrid their specializations to get what they wanted out of each specialization.
Hunter- Hunters had traps, pets, and a nasty nasty ranged attack. You could specialize in either marksmanship, beast mastery, or traps and survival. Or a mix of these of course. As a hunter you would go out into the world and tame your pet, each pet had advantages and disadvantages. They would gain power with you as you level, gaining new abilities and moves. In future iterations of wow the pets even had their own talent tree to specialize with. They had multiple aspect buffs. Aspect of the cheetah for speed, monkey for dodge chance, hawk for ranged attack damage, as well as aspect of the pack, to buff your whole party's speed greatly.
TLDR: All of the wow classes had their own interesting mechanics, fantasy, and utility/buffs they provided to the team. Whether it was rogue stealth openers and combo points and energy instead of mana, paladin auras/seals/judgements and specialization versatility tank healing dps, shaman totem buffs and attacks, tank heal dps versatility, mage buff and food/water/portals, warlock healthstone/soulstone, warrior rage/stances/shouts, priests buffs, healing / ability to specialize shadow for damage, druid the only one with a combat resurrection and versatility with shapeshifts and heals/buffs/spell damage/tanking, hunters with pets, traps, and aspect buffs.I know the classes are still early in design, I hope they have a similar level of fantasy RP appeal, and interesting mechanics that make them all very unique from the foundation of their design. Not just different abilities to use. I think the secondary class system is okay, however I do think the three specialization talent point system of WoW classic gives more player agency as to how they want their character to perform. However this is speculation as it is still very early in class design, let alone the augment system.
Check out how many choices you could make to hand design your class here.
https://classic.wowhead.com/talent-calc/