Tenth level kick?

[Ziggurat]

I've noticed in this game that around level 10, perhaps slightly higher, there is a perceptable increase in fighting and spell power. I have played about 8 games to conclusion but I lost count. Or, this could be my delusion since spell casters and fighters start accrueing enough points to actually start killing/casting alot better. Maybe this is part of game design: at this point you start feeling you can win these battles with less headaches. Before then, my lords, ninjas, samurais, bards, bishops, etc., seem to miss most of the time. Of course the battles get harder as you go, but there are few that really get out of hand later.

[Kakero]

no, it has nothing to do with your levels. it has something to do with how high your various skill is.

[Wereboar]

I've noticed in this game that around level 10, perhaps slightly higher, there is a perceptable increase in fighting and spell power. ... Before then, my lords, ninjas, samurais, bards, bishops, etc., seem to miss most of the time.

Look at your list. That are all quite slow developing classes.
A mage will become a quite powerful spellcaster at level 5-8. A fighter won't have such a jump at level 10.

I experienced it too that hybrid start to aquire spell power around level 11. Well, its like a level 6 spellcaster, but with worse int and piety, and less training. But then, around level 13, monster resistances improve, so hybrid spellcasting becomes quite useless again.