From what I tried, they need so many abilities to work and they STILL suck. They are simply underpowered. Nobody is going to care about splash damage that does basically nothing, there are better options for providing knockback, the Mercy Invincibility is actually obnoxious to cannons, and for God's sake, claws just laugh at their melee and staves mock them by 1HKing them when they can't even long range very well. Their usability needs to be fixed.
Here's what I would do:
*Nerf attack stars, from +~x/7 per half-star to +x/8. 6 Star weapons would have a multiplier of only 250% instead of ~270%. This is to nerf other weapons.
*Increase max health ratings. This would further tone down 1HKs, which other weapons tend to abuse especially when they have stars.
*Give cannons some freaking attack power. What they have right now is downright garbage. I should not need so many abilities just to have terrible DPS anyway.
*Increase weapon weight influence on knockback, preferably making the attacked person's weapon weight reduce knockback and possibly preventing ANY knockback (extreme case without abilities, granted). Not only would the cannons' high weight actually be useful for melee, but the Magnus Club would actually suffer as a side benefit from this.
*Double check the distance weapons that can still KO fast without ridiculous effort. Clubs are fine in general, since they already have to close the distance, but the distance weapons are not. They are EVEN WORSE for cannons than claws are--yes, that's saying something. And it's all because every time they fire the cannon user takes too much damage, and the distance weapon user can fire again and again, and retreat if the cannon user EVER survives the whole trip of coming close. Yes, yes, Reflect Barrier to reflect it, but does that ever work? That's the only thing a staff user ever has to plan against, and it's a stationary defense too. Compare to everything cannon users have to deal with.
*Nerf Petrify and maybe Freeze. Petrify's defense boost is so useful for the victim that it fails to keep low offense power weapons from utterly destroying him. Oh wait. That's not useful. That's a failed attempt at balance. The problem with these two is that they keep the victim from moving and make them a completely open target, not just stop their attacks altogether. These statuses need to be hit with the nerfbat. Otherwise, people will NEVER have enough incentive to use Super Armor over Aries Armor, since without Aries Armor, anything that is easy to hit will be susceptible to abusable status shenanigans, which as a club main annoys the bajeezus out of me.
*Nerf the invincibility skills, generally giving them big attack percentage penalties. They generally should be usable only for escaping, not for turning claws into blatant anti-clubs. Trade-Off should have reduced invincibility so that the user can actually be freaking killed. (Yes, Trade-Off provides invincibility, which IMO is stupid.)
*Slip Shot and Invisible Shot should have attack percentage penalties too. Slip Shot especially just for ignoring terrain, which shouldn't be treated like a joke. Invisible Shot deserves mention for being abusable with clubs.
*Lightweight should reduce weight by a considerable percentage. This would affect clubs and cannons the most because they'd actually be able to move around well and not suffer kiting. Anything that isn't light, meanwhile, would only end up suffering a defense penalty for a minor speed buff in a fast paced game.
*Energy Charge, in contrast, should provide less of an offense boost and maybe decrease speed for good measure (to prevent cheap escapes).
*Don't know what should be done with Libra Sponge or Bumblebee.
And for the record, I do not main any cannons, though the Ball Cannon may be a secondary. Rather, I main the Skyscraper Club, and wrote the Club Combat Guide in concern that clubs may be OP. Turns out I didn't have to worry about them being OP, because there are other things that are even worse.