Disciple of Khaine's ability states: "Spend 2 resources to redirect one combat damage just assigned to this unit to another target unit."

Would this ability allow me to re-direct the damage to one of my opponent's units? There are a bunch of abilities that are phrased in a similar fashion. Rules-as-intended would say to me that this ability is meant to deflect damage on to other units I control but rules-as-written would seem to allow deflecting the damage onto my opponent's unit.

Unless an ability specifically says you can only target your own unit, you can target anything. There are a number of nasty effects like this.

If you look at all the other damage moving effects you'll see the same thing so really RAI and RAW are the same here. Damage goes where you want it to go.