Beacon of Light puts paladins in an odd place, power-wise. In my view, Beacon breaks down as follows:
No Beacon = Underpowered.
Beacon healing one tank and one non-tank = Balanced.
Beacon healing two tanks = Overpowered.
Right now, the only thing keeping Holy Paladins in check is that they are abysmal at raid healing.
Blizzard has posted that they want to do something with Beacon in Cataclysm:
Currently on live, Beacon of Light is a tool that allows paladins to target more than just the main tank. In Cataclysm if it just doubles their healing, it is going to be overpowered. We have two ways we might handle this and we’ll experiment to see which feels better. The first is that Beacon only works on some heals, such as Flash of Light or Holy Light (but not the big one). An alternative idea is that Beacon increases the mana cost of a heal cast on a beaconed target, since you’re essentially getting a double heal. Under this model, Beacon itself would cost no mana.
The thing is that--as I understand it--healing is supposed to slow down a lot. Healers won't be GCD-locked, but more constrained by mana.
But here's the problem: if you're not GCD-locked, why spend 1 GCD to heal 2 people at double the mana? Why not just heal Person A with the first GCD and person B with the second GCD? It's the same amount of mana, but it's much more flexible.
I suppose the only allowing FoL to transfer is another solution, but is it really going to be worth the mana cost of Beacon? Beacon is actually a fairly expensive spell.
Traditionally, AoE healing works not just because it is time-effective, but because it is also cost-effective. If you can get full use out of your AoE heal, it is usually more efficient than using multiple direct heals.
Basically, I'm not really sure that the current Beacon of Light makes sense in the Cataclysm healing world that Blizzard is aiming for. It's been a godsend in Wrath, don't get me wrong. If we didn't have Beacon, I'm pretty sure that Holy Paladins would not be taken to raids. But in a slower, more controlled healing world, Beacon becomes extremely niche, with a prohibitive mana cost.
It might be best for Blizzard to just rework Beacon of Light entirely. For example, the new Healing Hands spell1 would match the name "Beacon of Light" superbly. In fact, Beacon of Light is a far more appropriate name for that mechanic than the current one. In the current mechanic, the Beacon target is more of a black hole, sucking healing in from the rest of the raid. With Healing Hands, the paladin literally becomes a beacon of light, radiating heals outward.
My recommendation would be to get rid of the current Beacon mechanics, rename Healing Hands to Beacon of Light, and either make a new 51-pt talent or a new level 83 spell.
1. Healing Hands (level 83): Healing Hands is a new healing spell. The paladin radiates heals from him or herself, almost like a Healing Stream Totem. It has a short range, but a long enough duration that the paladin can cast other heals while Healing Hands remains active. 15-second cooldown. 6-second duration.