I've  found  that  more  healing  and  less  damage  is  the  key  to  beating  higher  stages.  When  you  do  a  lot  of  damage  to  the  Ice  Golem,  its  Frigid  Vengeance  passive  is  activated  too  frequently,  and  it freezes  and  pulverizes  your  team.

I  only  have  one  high  dmg  champion  to  help  clear  the  waves  (fu-shan),  and  4  champions  that  can  heal/revive  (uugo,  thenasil,  minaya,  gorgorab).  Using  this  strategy  means  it  will  take  more  time,  but  you'll  be  able  to  clear  higher  stages  with  less  risk.

I  don't  have  Vrask,  but  I  hear  he's  an  excellent  healer.  I'd  lvl  him  up  and  replace  one  of  the  dmg  dealers  on  your  team.

maus mage is really good everywhere, 6 star and book him

Remove Coldheart. She doesn't do much in Ice Golem. Try getting someone with either Block Debuffs/Remove Debuffs and/or Dec Atk. 

Eventually, someone with Block revives / destroy gear to stop the golem adds from coming back, but that's hard to pull on auto.

Or maybe just try swapping some gear around to give your champs more survivability

Rotos is best for Ice Golem, he has both skills that work perfectly on Golem guards: decrease max hp and block revive (nerfed but still work).

You will need 1 or 2 champs like that, equip your champ with Destroy set -> decrease guard max hp, when revived they have less hp. 

Also you will need a block revive champ.