Wow... Unill they fix the glitch that'd be a very nice skill...
It is a curse and a blessing. Not caster friendly of course, but for people with small energy pools like me, a well-timed shield saves a lot more pain than it costs.
I would guess the skill would block damage the amount of energy you have. Then again, not too sure; that's a weird config for even a bug.
Nah I tested, I had Chop ice blast me for 5k damage in a duel. I only have 1k energy. When I put shield up, all the 5k damage was absorbed, and all my 1k energy was also gone.