Did this yesterday without knowing anything about it, jumped right into hard mode.
Really enjoyable. Best moment was the first "boomer": Loads of Zombies call for AOE right ?
Total chaos, couldn't see a thing, so many explosions ! After it was over i realize my tank is the only one still standing ... really a "holy ****!" moment
Bonus Boss is a bit hard, but thats oki its a Bonus after all. The other mechanics were easy to figure out, took us around one and a half hour for the first run.
TIP: Have a geared Healer and Tank and aoe your way to victory