hard time with mage - weak fireball and fire arrow

[lead341]

I have been playing Armored Princess/Crossworlds with a Warrior and a Paladin on hard difficulty. Currently I am playing with a mage, also hard difficulty, Level 5, end of Debir Island/beginning Scarlet Island - and I am having a much harder time than with the previous two.
Especially because on the one hand the mage has lesser leadership and also lesser Rage (I can´t use the pet dragon that efficiently) while the magic doesn´t really make this big a difference.
For example: I have 7 of intelligence and even invested in Destruction (+ 15 % strength of destructive spells). Even so my fireball only makes 170 damage - much less than in the original Kings Bounty The Legend.
Can this maybe be a bug? I realized that even with intelligence 5 the fire arrow also did only 85 damage.

greetings,

lead