It can be hard to get, but that shouldn't be because they kick your ass. It should be because you can't see them (or, if you're a svirf because they run like Tiamat is tracking them when they see you.)

At around level 20 you should have no problem with 95% of necros. If you draw the short straw and try to pick on one of Twist's morts, well, you're out of luck.

There's a good chance you know what I'm about to say, but I'm going to say it anyway: Know where people rank between 11-25. Know your way around these places. When you stick your head into Arendryl or Darsylon and hit "where" you should know whether they're close enough to run at now or if you need to back off and wait until they get closer to the entrance. You should know which entrance to the area you need to go to. A ranking mage is unlikely to be enlarged or flying, but they'll have groupmates, so run in, bash or trip and gtfo once they're dead.

Or, if you want Village app on easy mode, go Thug Thief. I think I had ten mage kills before I got inducted and I suck.