yep. Best you can do is make sure your attack is greater than their defense, and your damage is greater than their armor+health. Doing this will give you the best odds. Then there are the various buffs, but thats a whole different ball game. I suggest reading through the skill trees to understand what each buff does.
Um...that was the way it was originally implemented but it was corrected shortly after that so the lower level did not replace the higher level. Apparently, all the tinkering has undone that as well. *SIGH*