Private server players don't play on 1x for many more-than-logical reasons. First off, why would you want 1x in case you've leveled on 1x many times already, including on retail? People want to raid, they want to do end-game PvE and PvP. Having high rates is like having a second-grade character boost - it takes some time, but at least it's free. Second, what will you do and how will you feel when you encounter bugs which hinder your leveling process? What if some dungeons are closed? What if some scripts don't work? What if big chain quests end up not working (Thunderfury, Andorhal, the Sons of Hodir chain constantly breaks and glitches as well)? Third, in a game where leveling is hardly a factor anymore, why would you care about it and ask for it to last longer? You'll be spamming RDF from Crossroads/Goldshire anyway, while wearing half-heirloom gear.
"Yeah, but what about new players?" - WoW is 13 years old. New players are an almost-nonexistent minority. We have Medivh, we have Lordaeron - we saw what happened to them. It's good that Icecrown is full every evening so that people hop on Lordaeron, honestly. The most populated private servers are mid/high-rate ones, unless we're talking about vanilla where leveling is actually part of the game.
To the point: the only way a WotLK PvE server can reach Lordaeron's population is if it's mid/high-rate. Which kills the entire purpose of a PvE realm, to begin with.
Just no, no, no, and no.