I really like this card, and the idea of each element having a "bolt" type spell, a lot. I also think this should do damage to a player based on a players HP in the same way that it varies with a creature's HP. That would help to differentiate it a little more, I think.
As far as ideas for other elements:

: 2 damage per 10

that can also target immortal creatures. Cannot be used on an opponent.

: 1 damage per 20

to all creatures, 2 damage per 20

to all airborne creatures.

: 2 poison per 20

.

: my personal opinion is that stone skin counts as a "bolt" style spell with a healing effect.

: for every 10

you control, does 2 damage to opponent, 2 damage to you, or heals opponent 1 HP.

: life or light should do healing type effects (see below) Another option for life or light might be a creature buff bolt, like target creature gains +1/+1 for every 10 quanta.

: there's a poll right now on options to buff Holy Light where one of the options would be to turn into a bolt style healing spell.
http://elementscommunity.org/forum/index.php/topic,39386.0.html 
: draw one card for every 10

.