That's kind of the point. How often are your characters at full health? Do you multi-cast a cure spell every single time it comes around to a caster? I don't. Like most people I know the game very well -- I don't heal when it's unnecessary, and it's unnecessary 99.99% of the time that you have the opportunity to do so. If the characters had roughly 100 health max around the time you get Cyan, and the monsters' damage was scaled down appropriately, and he had 80/100, which would allow him to use his first Tech based on my mechanic, would he need to be healed? Nope.
Well it would make him useless during boss battles where it counts. I for one keep my characters at full hp during boss battles where they can wipe your hp down a fair bit and I think throughout the majority of the game I never go below 50% health