If you are on Herod, heavy consider going on Stalagg, I know my whole guild is having a vote about it sunday.
There's a group of guild that had a meeting for the Herod server, we counted nearly 10000 raiders. Without counting Good Squad & Grizzly, on each bring in nearly 1000 members. Plus all the random people and private server guilds.
From what i heard on the inside, Herod will NOT be an enjoyable launch with Insane queue's.
Again, I REALLY recommend not going to Herod.
I think Herod is the best choice by far. You should keep in mind that the surge of players will draw down significantly after a month or two so while Herod might be rough at the start I think long term you will want your character there because when the population does dwindle the other servers will end up low pop while Herod will still be high and playing on a high pop server in Classic will be the best experience. Server transfers will not be a thing I don't think.