For TBC new realms, at least some they should go for much lower populations like back then. Plus keeping an eye on the degenerated meta, faction balance - checking feedback from people with TBC pserver experience - as nochanges leads to degenerated experience on such servers.
Without faction balancing every TBC pserver was Horde server. With things like Paladins getting both faction seals and minor Ally benefits it was getting more evened out. But then we end up with drums uptime - back then it was somewhat on the top end / Muru. Here it can be quickly become mandatory or self-mandatory for parses (and then enchanting, jewelcrafting and whatnot) - to what extent Blizzard should care about this?
Plus for TBC they should have full patch data if they knew what a backup is (plus TBC zones stayed as is) so the question is how they will handle that. We likely start with initial pre-nerf content but classes/itemization of last patch (and like Kara reitemization?) or they will make actual patch progression with class reworks coming as they were in patches. This is a topic for another discussion but even a patch progression can cause some degenerated meta to abuse state of the game at given patch - really bad if like it would impact instanced PvP or gold making etc.
