I have found there is one thing I *HATE* about this game...
Even if a monster/another player is *1* level above you, you can barely fucking hit it! I missed 5x in a row against a level 20 Mage (I'm level 15 BTW).
A MAGE. She didn't Dodge it or anything, I just missed. I had the same problem fighting level 16/15 mobs when I was 14. That's utter bullshit.
You should see City of Heroes. If you're level 15, you can solo one level 16 pretty easily, two 16s or one 17 is hard. If the enemies are level 14, you can take like 10 of them no problem.