slanted difficulty levels, i was able to beat the final mission, but am still having a hella hard time on some of the infector ones (yes i have infect resist) and black hole ones
My best team was arbalest leader, engineer and air wizard supports. it works well because the arbalester does the most damage to single enemies with the volley of arrows, while the engineers bombs soften up just about everything on the screen, and the waves from the air wizard clean up whatever is left without me having to aim.
anyone saying lvl 20 was impossbile is prob using thei charge more than they need to. focus your energy on the bigger targets and the chain will kill the smaller