You need Vivianne (Mage) as Bodyguard. Basically her cast rotation would be 3x fireball, 1x blizzard... repeat...
I noticed that her casting range with blizzard is lower than the range of fireball. If you pull the mob on maximal cast range, she stops casting blizzard and you can stack her fireball dot infinite. By stacking the debuff you can kill rares much faster. Maybe even potential to solo Nok?!