Depends what you're playing. I haven't played any expert yet but it's easily done so long as your group is good. Speaking of good MvM groups what the forget is up with rookies thinking Natascha is worth using in MvM? The damage penalty is not loving worth it and the slowdown does jack stuff.
IMO Stock is best. Brass Beast is useful but the lower deploy time and movement speed while deployed kills me. The Huo-Long is useful on the waves with a lot of spies because the spies will walk in your ring of fire, get burned, and run away, but the Huo-Long also runs out of ammo super fast. I like Stock the best because since there's no advantages/disadvantages, it's really useful and easy to use.
Anyone want to party up? I just have 1 ticket left and I really want to finish Mecha Engine, I've only got broken parts left to do