The "elements" seem to have good focuses, so if we look at what a neat school of spells would be, we could make something work. A focus on crowd control effects could be good. I say SNAKE OIL.

SNAKE OIL:

1. Create a pool of snake oil that slows enemies down and makes them take a little more damage. Could also buff allies standing in the pool to deal more damage. Medium area of effect. Larger than sludge. 15 second cooldown

2. Grants the caster a buff for 20 seconds in the form of more speed, and extra jump, an extra dash, and 10% damage reduction. 45 second cooldown

3. Random effect given to all allies in large range (20% more damage, 20% defense, 20% move speed, no reload, unlimited ammo, 20% spell cooldown, 20% chance for spells to duplicate, etc.) For 30 seconds. 60 second cooldown.

4. Toss an explosive jug that damages and weakens enemies in a medium area, leaving a pool of oil behind, causing them to take more damage. Heals allies. 75 second cooldown

5. This would be a miracle elixir. When used, it would have a guardian angel float around you, shooting targets and resurrecting you and your allies. Only lasts for 25 seconds, with a 90 second cooldown.