The reason Gehennas is like this is because even though the population was already high, Blizzard messed up and allowed thousands of people to hop from Firemaw, to a dead server, to Gehennas.
Please roll these people back, as should have been done immediately when the mistake discovered.
That’s the old law of people want to go where it’s not too busy but if it’s too quiet they won’t go there because it looks dead and not good so people rather stay in the overcrowded area. Same happens with bars and restaurants. I guess we are like herd animals.