It does seem lame that Earth skills are left out. It wouldn't be a huge deal if they got rid of Earth damage entirely, but even a few more earth damage skills would make a big difference.
For the ability, how about another leech effect like Necro, where damage to armor gives you X% of your armor back? Say, earth damage leeches physical armor and poison leeches from magic armor? Though that would only make sense if earth damage actually damaged physical armor, which could be an interesting change.
I think a armor leech effect would be much more unique than a plain damage boost and encourage different strategies, like focusing on attacking an armored opponent instead of unarmored for the self-heal.
Regarding water damage not gaining a bonus from the ability, it's not a huge deal for me, since hydrosophist is more about healing and buffs. You still get a dmg bonus from int.
