Currently i don't like the way Essence is handled. You seem to have a very limited amount of essence and transferring it currently is not only a pain but also means you are unable to cast higher level spells yourself. I also didn't like the 1 to 5 essence transfer of beta 3.
Transferring of essence (imbue essence) should pop up a slider bar once cast this would allow you to slide the amount of essence you wished to transfer instead of having to cast it many many times.
Essence either needs to be more available and easier to obtain or the mana system needs reworked. Currently if you want to even be a caster at ALL you must spend every point you get from leveling into essence. NOT FUN!
Perhaps Essence should be looked at as the amount of power a spell has. The more Essence a character contains the more powerful his spells could be. Essence could still be gained the same way. Intelligence could be where mana comes into play making characters with high int better suited to be casters.
This would even pave way to placing essence into other things besides people like objects (Imbue artifact .2 essence) or even animals (magical horse).
Currently wisdom is useless because it only determines your starting spell points which makes it completely useless for all other characters besides your soverign and you can just increase your spell points with buildings and research. Why waist valuable points on wisdom?