No one in the world can make a twink private server with numbers (damage, scaling and efficiencies) that are actually the correct ones. I did the numbers for Hamcake land, but was kicked off the project before finishing tuning a lot of them, and this was using Live twinking (WotLK live servers at the time) to try and adjust numbers accordingly.
The smallest change in just one number on one class would unbalance things in accordance to how the actual balance of WotLK was.
People without thorough experience with the numbers, abilities and spells of WotLK and Private servers at the time probably won't notice a difference, but I can tell you no one will ever make a server that's actually like WotLK was.
I've expressed this before.
That's just the biggest concern I've always had regarding it, I'm sure the owners of XPOff have other concerns.
-lindenkron