I don't think this card needs a buff. It's great as it is! at least in a rainbow strategy.
I Think that the reason this card is so little used has nothing to do with it's impact on the battlefield.
the abilety to cast severaal earthquakes with one card is not to be underestimated.
No, the reason is that water and earth have little synergy.
there are no good
decks. That's why so litle use it.
The sollution should be to buff" the synergy between
rather than to buff this single card.
in fact, buffing this card by lowering it's cost or making it target shards would change nothing. It would make decks that allready use it more powerfull yes.
but it doesn't increase the number of diferent decks that use it, just because other than a rainbow strategy there are no possebilities to support it decent.