Coinich certainly has a big task in front of him. Looking at earth's matches, they have so many options, we will not be able to predict what they will do. We have no real way of stopping earthquake, we cannot use a pillars rush. I would count on quantum being in very low supply and needing lots of shields to stop the shriekers and the high damaging creatures to get past the shield which should be pa'd. So.... the only quantum generating non pillar cards we have are the devourers, so I would go with death/darkness. No mummies as rewind would turn them into useless pharoahs. But really, there is nothing hard hitting except the dragons and we need lots of death for that. Maybe try this.
Mark Water
6 freeze
6 chrysaora - needs 1-6 death per turn
6 poison - needs 6 death
14 death pillars
3 bone walls - needs 15 death
2 skull shields - need 2 death
Strategy is to use freeze on larger damage creatures. Poison as much as possible. Save enough death quantum to chain the bone walls when health is low. Skull shield to lower damage on smaller attack creatures while we freeze larger attack creatures. I would like 5-6 bonewalls instead, but they are too expensive when we will probably have to deal with earthquakes.
Everytime I come up with an idea, I try it out and it does not seem like it will work against earth.
The only other things I can think of is a death rush with earth as the mark and using all 3 of the enchant artifacts that we have. Or a death/darkness quantum denial/bonewall/plague deck.