Maybe it's HP, maybe something else - in any case, this is the first incarnation of DE and things like that just... need to happen, and be corrected, then something else is too strong or weak or both (yup! 'glass canon that is sometimes en masse on map' - kinda looks stupid, but the exact thing happened a number of times in many other games).

Anyhow, it's good to report that stuff and would be even better if you give some more specification - like class, ranged/melee perhaps something else... I'm 3/4 melee, and both Crusader (pure melee) and Assassin (pure melee and melee+ranged) find those... hmmm, perhaps more difficult than the rest, kinda bother, but manageable. But, hard - yes, even with 'artificial kiting assassin'. 

People with same problem (or WITHOUT it, but with some way how they overcame those) should post their stories...