I don't know if it's a translation error or bug, but the army drum only increases the morale of human units. I checked it ingame and in item.txt.

I think mage is way more difficult to play because he's so dependant of the randomness of scrolls on islands.
I mean, with some bad luck, you could never find any good spell like chain lightning, rain of fire, ice geyser, and so on.
With a warrior, you know you'll always find some very interesting units, in any game.

Actually it gives morale boost only to HUMAN troops (I think description is wrong)

I agree, I am finding the warrior easier to play. Putting the mana regens for adventure/battle modes at the bottom of the magic skill tree really slows things down for the mage. The dragon is pretty powerful too with the warrior. You can do a lot of damage early with its bottom 3 powers. I found myself hitting a new island perpetually maxed in Rage from battle to battle.

Yep in beging dragon > spells bvut in late game spells > dragon but leadership wins here in boss battles