is there a similar skill like templar's biting jabs for DragonKnigt?
One which also does aoe-damage, ist fast, doesnt cost a lot and maybe even heals?
Not really. DK has no channels in the class toolkit. The DK spammable is Flash Lash (morph of Lava Whip), which also has a situational proc for a harder hitting Power Lash with heal. Other damage/heals are Burning Embers and Deep Breath.
If your stamina, use shrouded daggers for cleave dmg, it will hit 2 other targets, the cost is only about 100 more than Crushing Weapon. Steel Tornado is really expensive and weak when not below 40% range where it's execute dmg kicks in.