(Just trying to figure out different possibilites with no mana regen here)
I think that mana should be a completely limited resource, potions and maybe a hub within certain castles and dungeons, like a rip in the veil allows you to pull out lyrium from the fade, like those lyrium stones in the deep roads and the fade from DAO. (Kind of like dungeons works in the Dungeons&Dragons MMO, where you have a place where you can stay and rest... ONCE per place per dungeon)
This would mean, you cannot just mindlessly use the biggest, strongest, most expensive spell to kill all the lowlevel foes at the enterance, as this would severely limited your mage until the later stages of the raid of the keep. But have the mage's auto attack do about as much damage as the archer. That would mean, that a mage doesn't become a burden if it is out of mana as it can still dish out a lot of damage. In DAO, I could do this, just cast firestorm then /dance until all is dead, and if something comes close, use Mind Break and walk around and use Cone of Cold then /dance again.
Another would be that spells are cheaper than previous games and with high enough willpower, you won't even lose 1/3 of your mana per encounter, but it would limit your damage output, but not the potetional. Since Quality = Quanity, (1*10 = 2*5), that would mean having a substainced damage potentional, rather than a highburst one. But in the end, you've done the same amount of damage
Also with limited Mana, we could remove cooldowns on most spells(Or have a gobal cooldown on all spells with like 1-2 seconds) , you could cast 10 crushing prison on all the enemies but then be out of mana and have to auto attack. Or you can cast 1 crushing prison, then maybe a fireball and Winter Grasp + Arcane Bolt, and then be forced to auto attack anyways. This would also, stated as above, make Willpower focused builds more useful, as you can have the same amount of damage per second as a magic build, but it would also have about the same %-cost in terms of mana. (One has 100 mana and cast a spell for 10 mana, the other has 500 mana can cast it 5 times, but each one also does about 1/5th of the one with 100 mana) This would open up a more creative play style with Willpower. Auto-attacks would still do more damage with magic builds compared to Willpower builds
While I'm not a game desginer on professional terms by anymeans. And I already know it is too late to change the mages balance by now. So my opinion is sort of irrelevant to the question at hand. But some of you were talking about it would make mages useless, so I wanted to post this just explain a way to get around it.
If anyone has any opinions or confusions about what I posted, I'll try to explain in better, as I'm not a native english speaker, so I probably burned the eyes out of the English-speaking folks here with my awful, awful
awful grammar.
TLDR:
1: I want no mana regan except places of power where you can restore your mana once per dungeon/keep and mana potions.
2: I want willpower to be an alternative to magic in terms of dealing damage and versitily builds, while magic builds should focus on pure damage and destrustion but can't do it very often
3: I don't want cooldowns on my spells or abilites as I find it a very arbitrary form of limitation on games, rather a gobal cooldown. Like if I take a huge leap, it will take me a short second to do anything else. Chain-skills could be possible, like "Spell X won't have GC when spell Y is used" Example "Fire Weapons + Arcane Bolt, allows you to use Fireball directly after" or "Shield bash -> Overpowered "
I think that's it. If you find me an idiot and had several flaws in my ideas, please tell me, you can't solve a problem by yourself, you need feedback.
Again, I'm not a gamedesigner at professional terms so I might have missed something critical, please point out that then.