1. I like, except one of them will need a new mechanic. Cause if you shift-click for earth blast you will just get earth kick because you just shift for that.
2. I like the idea of being able to bring horizontal earth. Since the two moves are very similar, maybe just delete Earth Pillar and add the horizontal pull to Raise Earth (Like you said), and then give it a new name. Cause now you're not only raising earth, your pulling it out from the ground. Maybe Earth Pull? The horizontal mechanic should be a left click. Basically the column mechanic for raise earth.
3. I don't understand how Drain would work for a passive ability? Because that move pulls water from the near by greenery into an attack move. Passives do not attack.
4. I think it would be more aesthetically pleasing and realistic if Element Sphere grabbed the elements around the avatar just like we see Aang do in his fight with Fire Lord Ozai. It would also be cool if we could put other people into Element Sphere like what Wan did to Vatuu to put him in the tree. I think I may have seen that somewhere so it may already a thing but I'm still give it attention here.
5. I think this is very reasonable since they have the same animation but one is melee and one is projectile. Maybe if you punch a person than the projectile is canceled and the player is ignited. Or, remove the punch. Because if you punch someone with the projectile it will have the same effect. No one would really noticed you combined the two move to be honest.
6. If Lightning Burst would to be made into a combo it would need a more advanced technique. The shift and release is too simple for a high level fire move. It's difficult enough to create 1 stream of lightning and now it's so simple to create multiple. UNLESS, you meant charge your fire burst all the way, then once fire burst is charged go to lightning. I'm not sure, you weren't really clear.
7. I think FireBall should remain it's own ability. Because fireblast is supposed to be a larger blast with more radius, where fireball is supposed to be a more precise, quick and intense fireblast. You can tell because it ignites the ground beneath it showing how intense the flames are. They are similar but they are very different at the same time in a way.