I have a purpose-built team to beat Justice league from when that meta was running wild on console.
I use Gorgotha, Khorvash, Amira, Wulfgarok (or Manticore if you don’t have Wulfy).
Gorgotha tanks against skull spams, self-cleanses (useful against freeze) and generates mana.
Khorvash mana drains Valkyrie and the top troop, and does significant true damage. He is a decent secondary tank if things really get off the rails and you lose Gorgotha.
Amira is generally a one-shot kill against Justice (first) and Mab (last).
Wulfy is impervious to protect against Kraken, boosts Amira’s true damage by 5 (10 against blue troops) and when things line up correctly, kills two troops in one blow. (Manticore is a decent substitute in that it is also impervious and gives a targeted mana-drain when you need it.)
Since the back two troops are immune to mana-burn, Mab is harmless against them. All you need to do is fill Gorgotha (preferably) or Amira (if you get a good red/purple board), kill Justice and then pick the others off as your mana collection allows. Even if the justice league gets looping a bit, Gorgotha can absorb a lot of damage and Amira does huge true-damage to the real threats on that team.