To beat the Dwarven Wall loop, you can use a few different things:
Burning pops barrier, so every turn at least one wall will be vulnerable to attack if you use a mass burn spell.
Mana Denial: The wall loop requires blue mana specifically; so if you get an orb changer who converts blue to something else, or removes/destroys blue, and keep blue mana from being matched, you can keep the walls from getting started.
Devour: allows you to kill them even if their stats get out of control.
True Damage+shieldpop: Assuming you can pop their barrier, true damage can circumvent their inflating armor values.
Exploders: If you explode the field, the skull damage will pop the barrier, then any cascading skulls will deal damage.
Skull/Doomskull Spawning: If you use a skull spawner of some kind, you can set up a cascade of repeated hits. Barrier will only protect against the first one.
Some of these are more effective than others, but this should be enough different strategies that you should be able to put together a team that can do some of them.