Barriers and recistance in nightmare mode singleplayer.

now after... lemme check on DA: keep real quick... around 54 playthroughs id wager half of them are full ones... and a solid 20% is on higher difficultys... aka hard+ now i played this game forever... but i never bothered to reaserch how certan things work... such as the tittle suggest barrier and resistances. now to my knowlage in nightmare (both mp and sp) all enemys with resistance will take one dmg from that element... aka fire dragon will take one dmg from fire mine... what im wondering in the resistance department is can it be countered, cus i been liking nightmare alot lately cus on casual/normal enemys just die to quickly to my godlike powers! >:D the only thing in NM thats bugging me is the resistances specificly while playing a mage. (as most the dmg there is "low end" spirit dmg or elemental. back to question though, can it be countered? say i specialize in fire (wich i do) and i am up against a fire demon .. does the "energy barrage" ability with upgrade counter it at all? 

i have tried testing it to little succes but i wanted to make sure as i only got it off a couple at a times until my comps killed the enemy for me. 

for the seccond and more "important" question i have searched around a bit on the inter web and found little, but i simply wanna know how does barriers work? not the equations but rather what "is" a barrier? to my knowlage its a shield that lose duration when absorbing dmg... but i am not sure of this.. the other thing i think it might be is a second health bar... in that case how mouch health?

generaly im not conserned with dying as i got quite a good setup but sometimes those pesky archers escape my tank and catch me offguard

*pffffffeeeuuuuwwww* *dead* 

now i am running a necromancer with guardian spirit passive and i seem to be oneshot even with said passive.. as confirmed by me turning into a ghost cus necro passive. this raise my question, cus after becoming a ghost my barrier from spirit pops on. does this mean barrier is a health bar? did it bug out? or did they just "penetrate it"? as i am wondering why use barrier if it does not negate dmg. (the big hits anyhow...)

to elaborate what happend was; i played my mage as mentiont earlier and suddenly i got killed with FULL BARRIER on. ofc DA:I beeing DA:I my companions DA:I-ed shortly after.. it is kind of annoying seen i cannot pass this boss without a working barrier on. paired with resistancees and well as i always say either good dmg or good defensives never neither. ... i do not wish to turn my trails/nm off as it kinda makes it to eaz ... to make an example im playing trails with the first 2 options (scaling and more abilitys) and NM mode and my fire explode thing oneshots normal same lvl non resistant enemys... having fire mines crit 20k+ etc.. turining down difficulty would make it ... ehh... i hate to say it ... as i love beeing overpowered... to easy...