Good news is stage 7 is not bugged, you may just need to level up a few more ogryn champions to help you pass this stage.

I don't know what your team stats are, but you probably need to stack your team with a lot more DEF. Go a little lighter on ATK.

I am not so sure defense will do any good. I am guessing the occult brawler has plenty defense for stage 7.

What I have experience with more than one faction has been the same. If it is the boss that attack with the adds.

It somehow felt like they ignored defense.

Just did a google searched and ended back on this forum credit to Shield Anvil:

I have pasted the mechanics according to his thread below.

What probaly gives you problem is add2 that ignores defense when attacking.

Blue Symbol:

A1: Attacks all enemies. Has a 40% chance of placing a [Fear] debuff for 1 turn.

A2: Revives all dead allies with full HP. Places a [Sleep] debuff on this champion for 1 turn. (1/4)

A3: Attacks 1 enemy with 2 random allies. Places a [Block Damage] buff on this champion for 1 turn if all allies are dead. Allies joining the attack use their default skills. (1/4)

Add1: Attacks all enemies.

Add2: Attacks 1-4(?) random enemies. Ignores (% of?) opponents DEF.

So my suggestion is, try to see if cc add2 will help you out.