You can stun enemies by letting them hit your block. Otherwise working together with the other villagers helps a lot as you already figured out. Sandwich enemies and either you hit them from behind or let the other villagers attack them when the bandits focus on you. Also only two enemies can attack the same target and they have an "idle" phase where you can attack. So only two enemies can fight you at once and with timing and stunning it should be possible to win. I'm not sure if I tried fully beating the game with the latest changes. You can move (rotate) while blocking to change the direction of your block btw..
I just finished my devlog where I write about the combat details and what was how much work: https://acurna.itch.io/village-defender/devlog/1462716/village-defender-postmort...
The "huge" terrain took actually barely any time. Surprisingly standard grass took a lot of time but otherwise it was mostly new stuff like the combat, AI and the quest system. It was an ambitious project with some things being harder and having more issues than expected but I got nearly everything done so I wouldn't really call it overscoped. I had an end screen in mind and a settings menu which I had no time for but that is about it. Besides improving/fixing things of course.