in dane is this mine where u can pull many mobs, during leveling all chars i made only at this spot 1-2 level just by aoepulling as much as possible.
for example with bard and heal it was nessecary to have concentration beside bloodlust too, when twenty mobs are hitting u makin it very comfortable.
with bard requiem and dancingblade was enough coz it is constant aoedamage on all mobs, with healer i had to use healcircle, shields and tearspells too coz heavenlystrike has cd and chainoflight does no aoe to all mobs, it was a clickorgy but funny
i would say u should have at least a bit concentration cuz like bloodlust it expands ur hp while doin damage in a way no other stat does over a long fight.
its a bit like the old warriorshield u have to break again and again and again before lowering the real hp.
with bloodlust u regain hp and with concentration u decrease the amount u have to heal up, in a constant flow of dealing damage and not getting huge damagebursts u so nail ur hpbar at a constant level, makes it easy for heals to react.
my gear is bäääh so im onehit for mostly evryone, but last sundaydomi there was a warriortank with 20k more kiki and he was wirling around and i got nearly no damage while i used meleeattacks and chainoflight to keep cleansingflame on him in supportbuild.
i have 12 items with concentration atm and try to get out how much items i can change back to lifepoints or absorb under 50%HP coz 12 is surely to much when gear gives more stats.