As brought to my attention and shares the same rule as Judgement of the Pure.
Benediction has a use, for the Paladins who don't go down deep into the Ret Tree, and do *not* plan on being Ret (Prot, Holy).
Having it this way gives synergy between the 2 talent trees. Both Benediction and Judgements of the Pure are beneficial to both specs but might not be the over all choice for the Paladin that chooses the spec when he compares the talent next to both of them (ie Imp Bom and Spiritual focus). This also makes both talents competitive when looking at all 4 talents. As holy a player that wants to spec shockadin they might question having a imp Bom to get a bit more ap for the conversion of in sheath of light that is a bonus for them because the bonus from sheath of light being a Hot is what they are after. For Ret it might question if the Paladin wants to have more of a chance at fighting push back for his healing spells assuring that he can heal if he needs too. Even though he wouldn't be able to do it very long or have a whole lot of mana it still gives the choice to the player giving them 4 viable talents to choose from.
Even though i do like your idea logically i don't see them changes Benediction to give a coefficient that would over all better some aspect in Ret and to be truthful imo i don't think one would be needed.
Not sure how Benediction got brought into this, that returns mana for judging and sealing.
I am trying to come up with a way to offset our overhealing that doesn't involve a HoT.
Here is the simple truth;
In a raid environment you will always have Priests and Druids using HoT's, duids in particular can choose to "consume" their HoT stack for an instant "big heal".
What this means is that when a holy paladin is doing what they do best (single target heal) they are constantly having the effectiveness of their heals descreased because of HoT's that are ticking and/or instantly transformed into a "big heal".
In essence, Blizzard has made us spammers on a lot of boss encounters, either of FoL or HL. I am fine with that, what this suggestion does is recognize that role and not punish us for doing what the fight dictated. Don't forget, as it stand now, in WotLK you get ONE mana pot in a boss encounter.
A Holy paladin should be the most efficient single target healer in the game, I want the 45+ talents to reflect that. I certainly don't want a HoT, thats a PvP need that is addressed nicely via Sheath of Light.
I see two issues with Holy;
The 45+ talents do nothing to improve our healing strength (single target healing), nor do those talents synergize with the rest of the tree.
All healers get NO benefit from our judgements, JoL and JoW should have benefits to the healers also.
They did address one of my biggest complaints as Holy, paladin is the only healing class that needs a Blessing on thier target to maximize healing.