The minion killableness of Flame Seed isn't as important, to me, as the zone-creation aspect. I likes me some battlefield control, and covering flanks.
As far as "Killing minions", it's far more on par with Scorching Burst. Same area of effect.
The only upside to Cloud of Daggers is that you can target a single enemy who seems interested in staying in one place (such as the target of a fighter's Combat Superior, or a Viper Strike). Not to mention that the single target in the center it hits isn't in the zone, but is merely attacked for d6 damage. Also, Cloud of Daggers can cover a single space, which is much better aiming (like say, covering a door).
As far as "Killing minions", it's far more on par with Scorching Burst. Same area of effect.
The only upside to Cloud of Daggers is that you can target a single enemy who seems interested in staying in one place (such as the target of a fighter's Combat Superior, or a Viper Strike). Not to mention that the single target in the center it hits isn't in the zone, but is merely attacked for d6 damage. Also, Cloud of Daggers can cover a single space, which is much better aiming (like say, covering a door).