I read over the word Diplomat several times, strangely.
The way you suggest, Dark Council gives points to a lone RW with Steeds. I have to think of a convenient wording of:
If your ringwraith is in a company with a non ringwraith character at a non darkhaven, non darkhold, non shadowhold site and each character in this company controls a Black Horse, Black Horse V or Steeds V (or a warg if an orc) this card is worth 2 marshalling points.
I do not see the need for more than one Black Horse, this is already enough of a combo to aim for. To have a really active ringwraith, you could add: ...and the company may move using region movement
Heralded Lord V
what about now:
If your ringwraith is a diplomat, he may be in a company with any other diplomat characters. 3 or more Black Council V in play give 2 MPs if your RW is in a company with a non-RW character and all characters in your RWs company control a Black Horse, Black Horse V or Steeds V (or a warg if an orc) whenever the company is at a non-darkhaven, non-shadowhold or non-darkhold site.
If your ringwraith is a diplomat, he may be in a company with any other diplomat characters. 3 or more Black Council V in play give 2 MPs if your RW is in a company with a non-RW character and all characters in your RWs company control a Black Horse, Black Horse V or Steeds V (or a warg if an orc) whenever the company is at a non-darkhaven, non-shadowhold or non-darkhold site.