Decided to sit down and start playing seriously for the first time. I will warn in advance that I am a big complainy nitpicker so if you don't agree with my opinions it's not a big deal!
Started with a Medicine Fairy build, had a really hard time, mainly because I think Into Delirium needs to do some poison damage. Anything minion or stronger is immune to the confusion and many enemy types (mostly ranged) are reluctant to switch targets to other monsters once they've seen you; not reliable enough to be her first skill.
Started over with an Okuu Hermit, got very powerful pretty quick. I was killing stuff way too fast so I switched on players 8 and it started taking a little more effort but after that it got really easy again. Even after I had already sank a bunch of points into Petit Flare, I changed over to Break Prominence and I can melt a whole room of enemies before they can even get to me. And the mana cost is so low I never have to use my normal attack. I'm not fragile either, kind of feels like being a Fairy but without the HP penalty. Flandre died in 4 seconds :V
Since you can stack Break Prominence it seems Nuclear Blaze Geyser is completely eclipsed by it in damage, AoE and mana cost. That's how strong it is!
General gameplay notes:
With a handful of exceptions, it seems completely wasteful to put your precious, precious skill points into unique stats when you can just slap on a hat and get +30 to it. Is this intentional? If so, is there any way to cap the hard skill level on these to 1 so players don't accidentally waste skill points on them?
Items giving large unique stat bonuses that have level 30+ requirements need to stop spawning in early game. These items will be useless by the time you are actually level 30.
I think it would be really nice if rings, amulets, and especially jewels did not spawn with unique stat boosts. The way they are now, the vast majority of these items are unusable by your character and you get enough of these boosts from your other equipment.
It's annoying to have so many different items and not knowing what class they belong to until the stuff is identified - this makes gambling kind of frustrating until you've already seen most of the items in the shops (for instance, buying a tengu shield to discover it is not meant for Aya). I propose adding icons to the custom item images to show who they're meant for. Example:

The Minoriko apple icon shows any Hermit can use it, while the Utsuho radiation and Aya fan signs indicate they are specialized for those characters. Preferably different classes would have different colors. This way you can know at a glance what items your character can use.
Since Pesco already asked me to help with item images, if he likes this idea I'd be willing to make these images myself (though I'll have to check how the item palettes work first to make sure this is practical).
Bug notes:
- Minoriko's Harvest HP bonus isn't working (also items that give a bonus to Harvest say "Harverst", coincidence?)
- Is the Paparazzi Cap unique tokin hat not supposed to have any abilities yet? (It spawned with strictly worse stats than my existing nonmagical tokin hat).