I believe it is a combo of rules with Ghaz. My opponent had a one page printout with all the rules as it was difficult to match everything up. So this is probably 70/30 confidence
However, with Ghaz's Whaagh, Ghaz got a 2++ and the rest of the army was fearless. (Friendly game to learn the new detachment)
It felt like Warmachine and aiming for a caster kill on turn 1 before the Whaagh could be called, as then my task became much harder.