Having played through the japanese deluxe version using a cheat, I decided to play this translation (bought from steam).
Not using an infinite HP hack essentially forced me to develop new practices and I noticed that the game's AI is incredibly good. So good in fact that I'd have to drill and practice for literally hours to match it (which I have not done and will not be doing).
And so finishing the game (much faster this time!) was simply a matter of controlling Sana and then spamming forcefield on self -> heal and more or less just staying out of the way. With buffs/debuffs and nukes for bosses (remembering to turn magic use to max before going in).
Later bosses had to be supplemented by pressing F2 and Sana healing, and had to use Life Dews and Revives for final boss, but it wasn't even as hard as when I had the HP cheat. Even final boss went down in practically no time.
Essentially, game AI Arche is so insanely powerful that you could just sit back as Sana, keep her standing, and watch Arche solo the entire first half. Stella may as well be an extra target and some interference. I lost her (and sometimes Sana) in boss fights and didn't want to waste a Revive so just played on. Arche alone is more than capable if you just keep healing her.
Not sure if this would apply to anything harder than normal, but playing as Sana certainly feels alot easier. But if you're doing higher difficulties than normal, you probably don't need to be doing this... right?