A lot of turn based strategy games can make good use of a minimax algorithm.
I think you've misunderstood both the genre and depth of involvement in the Dragon Warrior series. People don't like RPGs where the enemies are impossible to beat. Minimax is great for strategic games, but simple RPGs rely more on giving enemies cool-looking and overpowered abilities while leaving them with a fatally flawed strategy. The fun of that kind of game is finding the flaw in the enemy's strategy and exploiting it to beat them.