If someone stuck in a level, please, try this:
I completed both games Incursion and Incursion 2 without using a single mage unit.
Warhammers + Fire Archers = Win 5* in almost every level.
All you have to do is play once or twice to study what units are coming and place the defenders to the right spots...
And in a few levels (1 or 2 in each game) you must place some Ninjas for higher damage.
I did it, and it worked, just do not waste your time with overated AND overpriced magicians, specially in first levels, i hope this may be usefull for you guys.
Sorry for my bad english :)
 "Frozen Islands"){kind=icon}
 "Kick The Critter"){kind=icon}
 "Incursion 2: The Artifact"){kind=icon}
 "Villainous"){kind=icon}