The various elemental shields seem more trouble than they are worth as they are implemented at the moment- a 1 second burst of protection. It is difficult to gauge when to activate the shield given that its protection runs out so swiftly, and fiddly to keep doing so in time to bosses that keep spamming out attacks
change the shield mechanic to be constant: eg. as long as the shield button/key is held down (& maybe with a menu option to make it a toggle), the shield is active- during which it slowly drains mana. however, when it takes damage, that damage is translated into a moderate loss of mana proportional to the damage of the attack whilst to mitigate this, shields have damage resistance to their chosen element.
this might make sheilding more like regenerating cover and less like reflex-driven bursts of invunerability, and would work nicely with using shields as a counter to enviromental threats (eg. snowstorms, acidic pools/mist, cave ins, fire etc)