I'm at act 9 with my scavenger, leveling as arma/crema and it's pretty fun now.
The act bosses are no joke, I've never played a gauntlet event and I was under the impression this one wasn't a gauntlet, but I guess it is!
edit - lol, I just looked at the event page again and it was this little note: "Campaign bosses, as well as some Pinnacles have also developed a few new mechanics for you to overcome."
well, I thought they meant they'd have an extra attack or two, not be the entire pool of unique monsters you fought in the whole act.