Apothecary, Sethalia, Melga + 2 attackers
Kael (Lifesteal + Accuracy build)
Elenaril
Ninja
Skullcrown should be build for pure damage and campaign farming.
You need gear, dragon 20 should be your next goal. You will likely need the 3 support champs to get there. Eventually, as your gear improves you will likely only need 2. These will be slow runs, lol. But you should be able to clear 20 at 100% in a week or so. Plan on running multi-battles over night in dragon for the next month or so :)
1 - Old Hermit Jorge - Speed, Divine Speed or Immoral set
2 - Warmaiden, Uugo, Genzin, Seige Hulk, or Zargala - ACC, Stun, or Semi-Damage set
3 - Skullcrown - Damage set
4 - Frozen Banshee or Richtoff the Bold - Lifesteal set
5 - Sanguinia - Shield set
Heroes 1-3:
Their Mission is to kill Wave 1 & Wave 2.
Hero 4:
Only Mission is to kill Dragon
Hero 5:
Only Job is to keep Hero 1-4 Alive long enough to complete their Mission.