Simple trick to see what level a player from opposite faction is.
1. Inpect the target
2. Inspect talent points
3. Calculate hes level
Ex: I was on my 31 Ne Hunter when i saw a Ud mage. The mage had 18 points on arcane and 15 on fire
18(arcane points)+15(fire points)+10(the 10 first levels)=Level 43
The ud mage was level 43
This works on private servers to if you are able to inspect talent points or u don't get full talents from the start.
srry for my bad english : /