Originally Posted by
Elcura
Lightspeed is great for Stoneskin spam (WHILE MOVING) and Arise if Swiftcast is down. Defensively it's not useful for anything other than being mobile, if you want to cure adequately on the move Lightspeed is your jam. Like most AST abilities, plan it right and it'll be useful. A lot AST can do seems weak if you're just doing it on the fly without a decent gameplan (but that doesn't suggest that AST couldn't do with a buff in some areas).
You have to make a choice with soil to use a resource you could use for something else, it's more useful because it generally costs more than CC does. All CC requires is you to use it and it doesn't put you out of anything other than more CC.
So with smart use it's MP saving with no drawbacks other than you can't move.