You can see that the flameshield is only cast on my peon, so why the heck is it hurting my own flying units? Even in the instruction booklet, it implies that the spell only hurts land moving units. That has gotta be one hot flame, right? Why isn't my peon taking any damage :P.
Despite seeming useful, it really isn't. You are never going to have mage standing around with flameshield researched and blizzard not. Just use your mana for casting blizzard instead.