Some more facts:
Not every character does the same damage with the same spell. The order of magic power from weak to strong is:
Kieran - Timothy/Baccata/Lora/Paulson - Ak'shel - Conrad - Michael
Ak'shel is only slightly more powerful than Timothy and the others.
The fact that Michael is such a strong spellcaster is most likely a bug, imho; it doesn't make sense and it makes him overpowered. Why? Read on...
Note that the more damage you do, the more experience you receive. Because of this, when Michael reaches Mage level 2 (so that he can cast higher level Spark spells), he'll be a kick behind mage!
When your character levels up, you don't always receive the same amount of increased HP/MP. So if you just leveled up with Michael to Mage level 2, check his MP. If the max MP is 25 or higher, you can cast level 4 Spark. If not, you should reload and level up again.
After this, he'll even level up faster to level 3 than he did to level 2!
This also accounts for his fighter level, obviously. This makes it very easy to level up Michael.
If you have problems getting Michael to Mage level 2, you should do this: in Roland's Manor, cast Spark against the Orcs and retreat outside. Rest, re-enter and cast Spark again. Kill all the Orcs this way. After that, you'll only need a couple of more kills with spark to level up.
Conrad can easily make it to level 2 this way, btw.
The values for leveling up are:
Fighter level
12-25 HP
Rogue level
2- 12 HP
Mage level
1-6 HP
12-25 MP
18-37 MP for Ak'shel
I'm not sure about the fighter level's increase (the max seems true for most characters), the minimal MP increase (including Ak'shel's). Any confirmation is welcome!
k: