[Coda]

Sounds like I'd be playing mostly Water with those side effects. In a platformer, the Wind effect isn't going to be particularly useful, and the Fire effect is only going to be useful on things with tons of HP -- though since that includes bosses, this does suggest that Fire's effect is appropriately balanced.

I would consider other effects for Wind that might be more useful. I can see things like an air burst centered on the player to shove everything (including enemy projectiles) away as a defensive technique against swarms, or like Tornado Hold (MM8) causing the target to be momentarily juggled into the air so it can't advance.

I'm also not certain that 14% is often enough to make elements strategically useful -- at such a low rate, that's hard to use tactically because you can't be sure it'll proc when you need it most. Maybe instead of randomness, the side effect could be on a cooldown, and same-element bonuses will reduce it?

For a directly-controlled player character in a run-and-gun sidescroller, I think you'll find Power > Jump (up to a threshold) > Speed > Life > Jump (over the threshold) is more likely to be the priority for highly skilled players. Life is of minimal importance for top-tier players because literally every other stat contributes to never taking the damage in the first place. The only reason Jump has a threshold is because there comes a time when jumping too high or too fast becomes a liability instead of a benefit; aside from that, Power means the fight is over sooner (and therefore less opportunities to get hit) and Jump and Speed let you avoid incoming attacks and place your own more precisely. Life is a dump stat for when you can't get more Power and your Jump and Speed are already at the highest useful level. (Meanwhile, Life is probably going to be the MOST valuable stat for AI-controlled allies because you can't make them dodge, with Power being a close second and Speed only being necessary to keep up with the player-controlled character.)

How do those skills actually work? Do they need to be actively triggered by a button, or are they passive? How often can you use them?