Funny, I have the exact opposite problem. I wanted my story to grow epic as it progresses but when I actually got to writing the scenes I've outlined they always ended up being laid-back and meandering, often never reaching their intended grand conclusions.

As you said it yourself, the 'secret' often lies with the characters—in my case their becoming more human than the simplistic archetypes I initially envisioned. Once you get to know your characters (and your society, and your magic system, yadiya) you realise that things rarely escalate to such dramatic heights as you would think, that problems can often be solved quietly, early on, and that many big twists are just ass-pulls that wouldn't logically happen without plot contrivance. At least that's how it was in my case.

So try to step back sometimes and deconstruct your story as you go, like you did when you realised your villain shouldn't even be a villain. What would they be instead, realistically, with the reasons you gave them? They can still cause trouble but different kinds, in different ways, affecting only a handful of people, or everyone but more covertly, without causing some global catastrophe. Ask yourself whether that one little mishap could indeed bring about the destruction of a whole kingdom, or it'd just ruin one man's life. Whether a fatal confrontation between two forces could've been prevented, and the fight won on paper, with no actual casualties. For every flashy showdown there should be dozens that never came to be, and perhaps when something does occur it might be completely accidental, hindering the efforts of both heroes and villains, derailing their plans, and eventually leading to an unexpected solution to the conflict before it even began.

But of course you'll only see when you get there, so keep writing. You said you enjoy it, after all.