No, by default in most RPGMaker games item use is an action in battle. There's probably a way to tweak that, but I'll probably leave as-is for now. The smaller healing items are minimal in their help in battle, but not completely useless: one should often be just enough to buy one or two rounds more than you would have had otherwise, though obviously they become pointless if there are a lot of enemies still attacking. It's certainly arguable they should be a bit stronger though, and something I'll consider as I keep working on chapter 2.