Divine Intervention is a very weird spell. The spell itself is a terrible, terrible mechanic. You can only cast it on another person, who must be a resser AND in a position where she won't draw aggro when the fight ends. Compare that to the Warlock soulstone, or Shaman self-res. And yet the flavour of Divine Intervention--the paladin sacrificing herself to save her companion--is so strong, that the spell somehow works.
In reality, the major use for Divine Intervention is to help the paladin avoid a repair bill. It would be nice to have DI do something useful, while still retaining its flavour.
Tharok and I were talking about it, and came up with the following:
Instant Cast, Reagent: Symbol of Divinity, 100 yards range, 60 min cooldown
The paladin sacrifices herself to return all other dead group members to life with X health and Y mana. This spell can be cast in combat.
So it's a combat res, but the paladin has to die. It's possible to get up to a 4 for 1 trade, but you can only resurrect people in your group. You'd probably need to combine this with preventing groups from being changed in combat, and maybe give druids a real resurrection spell as well.
Edit: Actually, Divine Intervention is a really interesting spell from a design point of view. The key element of the spell is that the paladin has to die, to sacrifice herself. However, the paladin is often the healer or the tank, and usually when the tank or healer dies, the group wipes soon after. So you need an effect which makes a large impact, and can lead to the group defeating the fight, but which overcomes the extremely large drawback of losing the tank/healer.