Enemies do hit hard! It's to make the game challenging without throwing lots of fights at you. I've mentioned it before but there's no "Easy" mode, there's "Casual" mode, which allows for more room for error and some extra healing and potions, but it's by no means designed to be easy.
Stuns and other disabling abilities do affect enemy stats. The trick is to add multiple stacks of them, not just one, to get a big effect. From feedback I've gotten I'd say the Stunned status is by far the most useful tool to make rough fights easier. It can stack up to 5 times, and each stack reduces all enemy stats, allowing you to hit harder and making them hit you for less!
As for needing a lot of potions, have you given the potioneer some craft kits to increase your potion total? Also, there are a few healing abilities that Celia can learn, and some that reduce damage taken! These help immensely with sustaining your health through fights, and will save you some potions in the long run.