Well, I found just one in-game glitch: If just after casting the ability I move the hero anywhere, the Thunder Clap SFX will be spawned not under the landing unit but about the middle between the hero and this unit. You should replace somehow the position of this SFX.
Well, now, about possible improvements (Of course, this is IMO): I have only one, you can make explosions be different on ground and in water (Just for eye-candy), leave it a Thunder Clap SFX on the ground, but if the unit is dropped into the water - let it be Naga Death SFX.
Your codding seemed fine to me, although I didn't look deeply into it, cause I know you as advanced spellmaker and you know how to use loops, indexing and remove leaks.
The thing I personally dislike (So I can't complain on it) - this is your style of makin Custom Comments in the triggers, but, well, that's the matter of your personal choice, maybe not such a common as we usually use, but okay.
Oh, and one question:
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Animation - Change FS_target[index_loop] flying height to FS_constant[index_loop] at 1000000000.00
Why such a number, not zero?