I think an othell spoiler does from facing dmg better with self pom and plunder.
All othells will 1 shot pve mobs solo with the correct gear. In afk macro, even a ghost hunter will 1 shot from the front with Heartbreaker, chain blow and shadow reverse will 1 shot from the back (stabbing the front).
I'm surprised you aren't considering wind rider. It's 2 special stabs always get the flank bonus and reset their cool downs. It dishes out dmg fast.
My biggest gripe on adventurer is the front facing bonus. You will still use shadow chase to move, and still utilize the back. In practice, the adventurer is the worst dagger imo. You don't need mp, and the front facing bonus is weak compared to the flank bonus of a wr, rear bonus of a gh and/or self pom and forward bonus of spoiler.