Therees a couple of things you have to take into account here i think.
1. Spellcasters seem to scale better so that at higher levels they get immensly more powerfull than meleecharacters.
2. Spellcasters fill other roles than simply doing dammage, they have tons of utility and support that benefit not only themselves .
I can defiantly see where your coming from thou as i often find my priest and mage only casting cantrips or using bows in many fights thus feeling somehow unneeded as my warrios just jump anround slaying everything
But in some encounters they are invaluable and definatly the key to sucess, i am pretty sure the latter will be more prfound when they level up more.
