To me, it is not unfair to go against a higher level wizard if that wizard is the same rank in PvP. If rank is a reflection of skill level, and it is supposed to be, then matching up against those with the same rank or slightly higher is a match against someone with a similar skill level, and that is exactly what is called for.
If you pvp late at night there are less people on and therefore sometimes the matches that you are set with; they dont really work.
If your rank is really high say 800-1100 you will be getting higher levels because ki wants to give you more of a challenge. If you have try all opponents on, it kinda speaks for itself, you are trying all opponents. If the people you go against have low rating it doesnt matter how high your rating is, they will get lower levels to give them an easier fight.
If none of these are whats happening i dont know what to say, your game must be glitched.