This new difficulty is fairer, but I actually somewhat enjoyed the original difficulty of the late 2 levels on their initial release. They took a few tries, but if you payed attention to what lanes were the problem and adjusted accordingly they were plenty doable. Since there is a normal mode atm, I wouldn't mind seeing a hard mode with a few levels of that difficulty in the future. That or maybe a few of the late game levels have a similar difficulty level. Just so long as its difficulty that can be beaten with strategy and not just grinding unit upgrades.
Also it seems like your ranking is based on exclusively how many units you lose and scales in flat amounts (0=S, 1-3=A, etc.) when it should probably be adjusted on a level by level basis. Losing just 3 units in 2-10 is a lot more impressive than in 2-1 after all.