Why are villains much harder to defeat than heroes?

[Wolf Kanno]

So that means that while heroes just tend to attack straightforward, villains tend to use more advanced tactics...

That's kinda it in essence. The heroes have their own advance fighting styles but I think (for me at least) you learn how to utilize said moves more when you start using the villains. Squall for instance is a character whom Block is imperative. Also the villains teach you more about exploiting range better.

Using Terra, I don't have trouble with any villains except Ultimecia. The guys who really hurt is when I come up against Onion Knight, Squall, Tidus, WoL, Zidane, y'know the ones that dodge their way in and then hit you really hard, then combo with an HP attack. Doesn't help that melee are pain trains if they touch you and all the ranged characters are only about half as strong, I say the ranged should be stronger because they are easy to dodge.

This is why Terra has unfair HP attacks, Tornado is her "ultimate defense" move even able to reflect back her reflected spells if timed right and the computer backs away from it as hard as it can. Flood is tricky to dodge and an Uncharged Meltdown is wickedly fast and easily takes out dodging scrubs like Zidane and Tidus. Not to mention when its fully charged it will either start ricocheting around the arena or actually home in on the opponent. Holy is also difficult to dodge if you attack them from directly above with it...