One thing I'd do is play around with the starting values and divide/multiply all of them by a common number.
For example, let's say in the default database, Enemy "Ghost" has 100 HP, 40 ATK, and 40 DEF, and Actor "Arshes/Aluxes" has 200 HP, 60 ATK, and 60 DEF. If you think 200 is too high a value to start out, and want to lower it to 50, then you can simply divide all actor and enemy stats by 4. So now the "Ghost" would have 25 HP, 10 ATK, and 10 DEF, while Arshes has 50 HP, 15 ATK, and 15 DEF.
If you do that for all the enemies, it should be fair and balanced enough.
Now, after doing this, you can start modifying enemies to have more variety. For example, give an enemy a higher attack but a lower HP and Def; or a lower attack and medium HP, but high evasion. Just play around with the values and keep testing the battles. Soon, you'll have a good set of enemies for your game.