I'm increasingly feeling like overreliance on "cooldowns" as a balancing mechanism leads to stale, boring and annoying gameplay. I don't feel like AVWW has that problem right now, mainly because the cooldowns tend to be more like retroactive "cast times," with a couple of exceptions like summons. I'd like it if it could not skip further down that path, though.
I'm not sure what gameplay purpose shields are meant to solve, exactly. Something you use to avoid a strong and otherwise unavoidable attack? Maybe a mobility penalty would be more appropriate, like not being able to use or trigger the shield while moving, and unable to attack (while keeping the existing mana cost). I'm sure that has its own downsides but it seems like a reasonable alternative to me.
Unable to attack while using makes sense to me.
Unable to MOVE would probably just be a bad idea; they'd go from useful to pretty much useless.
I do though think a high cooldown is a much better idea regardless. It completely stops simply spamming them, without removing the possibility of combining them with other spells (like using it to get close and Ice Burst something).
The problem I'm having is the realisation that the games with really enjoyable combat for me tend to not have cooldowns. Like, at all.
I think what you said up there sums it up well: they're attractive because they're really easy. You just put a cooldown on it and it can't be abused! It's the simplest solution imaginable - it works, insofar as it stops players from using creativity to break your game balance, and it saves you - the designer - from having to come up with something actually interesting or integrated with other abilities at all.
If something is going to be in the game, it should be integrated well with the other systems such that it promotes interesting, thoughtful, dynamic use and gameplay.
So, to throw out an example: what if having a shield up halted your mana regen (but it had no cost) and having a shield up halted your shield power regen? Then you've got two contradictory forces at work that hopefully interact with the other systems well and promote cool and interesting gameplay.
Unfortunately, that solution (while not a bad idea) would only work if mana recharge rate were DRASTICALLY reduced.
The thing about cooldowns in this game, is that, for the most part, they're not GLOBAL cooldowns. They're for individual spells only. I dont even look at them as "cooldowns" much of the time. I look at them as a rate-of-fire kind of thing, because most spells that have them to where you actually have to pay attention to them, are attack spells; utility spells like Sunrise or Ride the Lightning or Light Snake do TECHNICALLY have cooldowns, but I honestly never even notice those; they're very short and unobtrusive. Utility spells just dont really NEED them, so they're nearly unnoticable there. And of course these can be altered with enchants.
Any combat spell though, or anything that may for any reason potentially be useful in some way in combat needs to have it's rate-of-fire (or rate-of-usage, however you wanna say it) kept in check. The moment you start to remove this, is the moment when the game's balance starts to completely break down. As it is, using more than one spell allows you to get around this a bit; you fire Energy Orb, right, and it needs a moment before it'll fire another bolt; well, during that time you can cast another spell, be it Forest Rage or Fireball or whatever. The game doesnt stop you from doing this. And on a technical level, pretty much ANY game is going to use this concept. Even something like Contra generally has limits to rate of fire, or with some older games, rate of "how many bullets you can have onscreen at once" which creates the same effect in the end (but also allows for a certain exploit). Look at Castlevania; that's a classic game, with combat and platforming that required alot of precision and careful movement rather than just wildly hopping on everything. But Simon Belmont did in fact have a "cooldown" period that he had to deal with, in the use of his whip.... you could only use it so quickly (which wasnt very quick at all). Even his special weapons were prone to this; you had to wait until each was off the screen before you could toss another, unless you had the multipliers of course, but even then there were limits.
The reason why this is so important for the shield spells is because they basically act as a seperate, temporary health bar every time they're used; this temp health takes damage instead of your actual character until you either run out of mana, run out of time, or the shield is overwhelmed.
The problem is not the cost of RUNNING the shield; the usual situation with shields is that they pretty much DO stop your recharge while being used, because they're a constant drain; sure, you can attack or use other spells while they're up..... but you're going to simply drain your mana pretty fast doing that. (characters that can do this WITHOUT draining are likely just unbalanced at the moment). These shields are pretty powerful, and they need cooldowns for the same reason heavy attacks need them. Look at Ice Burst for instance. This one hits HARD. Melee only, but HARD. If it had the same low cooldown as, say, a Forest Rage, particularly Forest Rage with cooldown-reduce enchants on it, Ice Burst would then be WAY overpowered. You'd have to either dramatically (really dramatically) increase the cost of the spell, or dramatically lower it's damage in order to balance it WITHOUT increasing that cooldown. In that same way, balancing the shields out a bit better WITHOUT some limitation on how often they can be fired up would require lowering their various stats, increasing the rate of mana burn.... things that in the end, would mostly just come out kinda annoying and reduce their usefulness.
I know what you mean about "games without cooldowns" and I can think of a few..... but those few tend to be pretty darn mindless, in how the combat works, and only have a very few attacks (and often have alot of nasty exploits).