Way to kill gold eater without killing the heart: 1) Block the magician 2) Save a lot of energy for his 5 energy costing skill 3) get the priestess to heal people with low health The magicians attack do 2-3k each and he has around 2 hits per turn
In the second one I just used the Hanged Man cause he reminded me of Eeeyore from Winnie the Pooh. You circle your team around a square far away form the action, and then Hanged Man delivers a gold eater to you like pizza. Then you just let everyone attack it. By the time you're finished the next one is ready. I won this way in just 4 turns against the Second Beholder Battle. Hanged Man does 8-10,000 points damage on his attacks against the Beholder.