Look at this.
I sacrificed two heroes to the first floor. Second floor was full barbarian team and they blew through TWENTY HEROES
The invincibility makes it a ridiculous meat-grinder of seeing how many turns it takes before Drak gets up to his 8 HITS PER ATTACK at double damage from balog’s rage buff. They don’t even have any healing, except for Drak’s incessantly regenerative uber-field-dressing. There is NO GOOD REASON that they should be such juggernauts.
Twenty heroes. All level 70, 6 Stars, with runes. This does seem to happen every time you bring out a new hero type doesn’t it? Maybe do some research next time before releasing another half-thought out, system wrecking update? “Dungeon Boss just got better!”