I soloed Omen as a lv 20 Free Trial.

How did I do it? Kiting.

Kiting kiting kiting kiting.

First I noticed that omen doesn't regenerate after each combat like other mobs. Then I noticed that omen is pretty slow for a boss and can be outrun by practically any speed buff. So I combined running with instacast spells like Frostshock and Flameshock and after a few hundred resets: