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Aye, I think the spells and such need some more balance yet. Some of it, though, is going to be dependant on the player, which can make this tough. For example, you mention Campfire being just okay.... but in my case, Campfire is 80% of the reason I use the spell set, with Flameout being the other 20%. I've found that most of the tier 1 classes are REALLY AWFUL and simply cannot get the job done most of the time (particularly any class with one of those blasted charge spells). Flameout is also the only major high-damage spell at that tier, and on higher difficulties (I'm on hero currently), this isnt just a good idea to use, it's a NECESSITY. Bosses on this difficulty are basically impossible without a spell like this, as their patterns are literally undodgeable, with the only exception maybe being the sine attack, and even then, it's really bizarrely easy to get hit by that alot ANYWAY. The one, and only, strategy that I've found for beating bosses on this difficulty is to pump up full of health and ammo-attack perks, choose a very heavy damage spell like Flameout, and just crash through the boss's shots and blast them point-blank with it. Nothing else works.... heck, nothing else can even HIT them most of the time.
Since Campfire and Flameout are so good in my view, Embershot being kinda weak is fine by me, balances it out a bit. I do find though that while I dont consider straight shot spells to be all that great, I do attack many types of enemies with them. The enemies that that does not work on either get hit by Crescent, blasted by Flameout (usually those accursed balloon things with the spiked balls), or sometimes I'll use Campfire to enhance my chances of hitting with Embershot (I'll do this more often than the other two options). The straight-shot spells arent very interesting or powerful, but for this sort of game I do think they NEED to be there. But there might be a few too many of them.... there's an Entropy-based class at tier 1 as well, and that one has not just one, but TWO straight-shot spells.... and THAT doesnt work very well. Straight-shot is fine to use, but in this game you NEED more options than just that.
Aside from a few spell types being useless, or at least SEEMING useless (bomb types are a good example... I only JUST NOW found out how to really use these, and what sorts of foes to use them on; their tiny effect radius makes them very hard to use), I think the main balance issue right now as the spell classes go is their calibers. More spell classes need better options for dealing with enemy shots, and they need some options that ARENT just ammo spells. The caliber system itself is very good; but the actual numbers on various things are what needs tweaking.
Not just that though.... many enemy patterns need altering (or outright replacement), particularly as the difficulty goes up. Like this Clockwork Pigeon thing. On Adept, it's a pretty normal enemy. On Hero, it's a nightmare; you either have a very high caliber spell, almost always only ammo spells will work on it, or you *will* get hit. There's no exceptions to this. You WILL get hit. It's pattern is utterly undodgeable in the sorts of areas it appears in (almost exclusively buildings, the worst possible type of place for anything that spams a zillion bullets). Much of the time, when one of those horrid things shows up, I either have to spam ammo shots till it pops (usually crashing through many of it's bullets to get to the right place to fire), or hide behind things until it goes away. It's attack pattern is OK for normal difficulty.... but it scales so badly at higher ones that it's utterly broken. You cannot dodge it's attacks because there is literally no SPACE in which to dodge them, and you cannot hit it with ANYTHING that doesnt break it's shots, because there's no space for your attacks either. This particular enemy is a pretty extreme example, as there arent many enemies that are THAT spam-tastic, but there are some, and that blasted bird is unusually common. On difficulties even higher than Hero, I'm betting there are more that get broken.
Bosses are the worst though right now. There's a couple of problems with these guys right now. Firstly, most of their patterns are pretty much broken. It's like the thing with the pigeons, there's simply no way to dodge because everything is clustered so tightly and fired so rapidly (on Hero, again). My one and only strategy against these guys is crash into them, go nuts with strong ammo spell, hope to not die. Most other spells are literally incapable of hitting them, no matter what goofy angles you fire at. I know these guys arent finished, but the current patterns arent even good starting points; frankly, the bosses in the previous game were much better. There's also the irritating bit of having to WAIT at the start of the fight every blasted time for them to walk AWAY from where I'm standing; there's no point in attacking them when they're super close. You want SOME room to move after firing the ammo shot to reduce the amount of stuff you gotta crash into. To be honest, these guys should almost just be disabled until they get fixed. They're THAT broken.
There's other stuff to go on about, balance-wise, but I'll go into it more after more testing. I'm liking most of the new enemy types too, by the way. Though those urban droid things.... crap but they're ANNOYING! They're currently the ones I'm now using the bomb spells on most; hard to time that, but it WORKS. Goddamn bats, indeed! I am finding more use for some spells now that previously did not get used much, as more and more new monsters show up. A very good thing.
EDIT: One other thing: Bosses.... just a BIT incredibly ridiculously annoying to find in caves. Due to their unbreakable patterns, I *have* to leave the cave, going back aaaaaaaaaallllllllllllllllllll that way, to go grab whichever spell class has the "boss wrecker" ammo spell for that tier, and to change up my perks. Caves are pretty tough as it is.... I dont think these guys need to be here. At least not until they've gotten some MAJOR changes. Leaving the caves takes SO long that what I usually actually do is just die, and never enter that cave again ever. Easier and less extremely aggravating to just go find another cave.
EDIT 2: Actually, I'm pretty sure this particular cave is unbeatable on Hero. Completely unbeatable. The ONE spell that might kill that guy (and again, his shots are absolutely undodgeable) is in the blasted Littorist set, which is completely worthless in caves (aaaaagh charge shots, why do these exist). He's impossible to even hit with anything else, but the other 4 sets are the ones that could GET to him; Littorist simply cant. Yeah. Bosses.... just a BIT broken right now. Pretty annoying.
EDIT 3: Oooookay. The pigeons are NOT the most broken thing on this difficulty. These things that look like werewolves are. Pigeons are technically dodgeable in big, open areas.... these wolf things AREN'T. Instant strike attack (like the Crescent shots, that sort) everywhere around them with monstrous range (most of the screen!) and very rapidly fired? ......Yeah. Right now, any area that has even ONE of these is probably unbeatable. Hmm, I might have to actually start a new world yet again.... I'm finding that Hero, at least, may be too broken to play through. Far too many screwed up enemies.