'Marked for Death' anoint not working on mercenary

As far as I know mercs can benefit from anoints, but Marked for Death doesn't give them culling strike against targets that you have marked for them.

The wording is just 'Culling Strike against Marked Enemy' so I see no reason as to why it should't work; if it said 'Culling Strike against enemies you have marked' I'd understand but as it's written it should give cull against any marked enemy.

Wasted a silver oil in ruthless in order to discover this.