Simple, make it castable on allies as well.
- Using them on clashes are hard enough as it is, or when you are suddenly pulled in by anything.
- They do not affect/damage allies anyway, thus using them while an ally is chasing the enemy ruins your aiming.
- Also, spells like Breathe Fire/Carrion Swarm/Shockwave are naturally like this.
- This is imba.
End of suggestion.
If there are no more delivery spells available (overlapping base skill issues courtesy of Blizzard), just use an AOE spell, then change the targeting cursor to that usual single target crosshair.
Then, when the spell is cast, find a unit within some small area nearest to the target point of issued order, if its an enemy, order the dummy unit(s) to cast their skill on them (for the Macropyre/fire part of DB), if its an ally, cast it on the target ground.
P.S. I am also aware about Dragon Slave, Light Strike Array, -_-...