[Chaos]

The Elemental Augments are practically useless beyond Blazing Shinken, Quaking Heaven Kick and some of the skills with Talvyd (iirc the one that increases range). You're donning a weakness for what, some meager damage with a good chunk of the applicable skills? It doesn't make anyone want to bother with any of those skills.

That being said, Quaking Heaven Kick is perfectly fine as it is; you are pressing Knockback onto an distance-closing skill, and if they happen to have a way to counteract the knockdown (Kip Up and/or On Guard), you're just stuck with a weakness. The options here are accessible enough to where if someone is really adamant on not getting either, it's their fault when they get caught in a knockdown loop.

....And let's not boost the range requirement. If any enchant should be boosting HK's damage significantly, it would be something like Redgull.