Trash mobs more dangerous than Rares

So many times while I'm fighting a rare mob I get one-shot by random @$$ trash mobs surrounding. They either use some ranged rapid fire frost attack that crits me or any other ranged or spell hit that one-shots me. I think this is a factor of the new mechanic of reducing mob counts and stacking power into the remaining mobs. I am CCing and jumping in on the Rare assuming it to be the most dangerous thing on the screen that needs to be CCed and dealt with but the trash mobs are just as strong if not stronger than the elite and one-shot me with 1500 life, 1700 ES, and capped resists. While map mods are nerfing my potions and defenses and these elites have passive period damage crap that goes off even when I am CCing them. Why do you hate melee!