The restrictions are: they need to have both sides must have a chance to win (no auto d1), must not be just for achievements, uses less than or equal to 2 guns, and have an average completion time greater than 5 mins. With a few other things.
Also, this brad guy said he wanted to blacklist sleuth shaming for being town-sided, please stop him.
The blacklisting would be less random if you appoint one mod with a proper understanding of setup design to take care of the permanent blacklist and let the other mods who think something might be up temporarily ban things until the blacklist mod is there to pass final judgment.
That might be it. I went back and three of the last four games were indeed very short. In the first one the spy played like , in the second the traitor thought it was optimal to get lynched.
Only the third game had a proper speedlynch. A noavi claimed spy because he wanted to pew pew. That can happen in any hunter setup.
Most vengefuls I've played were perfectly normal, though.