Um, what? You are far and away wrong, Blackbriar. Eternal Flame scales entirely linearly.
If I hit myself with a 1 point EF, I get healed for 28k and get a 6k HoT. Both apply Mastery.
If I hit myself with a 2 point EF, I get healed for 56k and get a 12k HoT. Both apply Mastery.
If I hit myself with a 3 point EF, I get healed for 74k and get an 18k HoT. Both apply Mastery.
(Bear in mind, the HoT numbers above are double normal because it was self-cast. On a fellow party member, the numbers would be 3k, 6k, and 9k ticks, respectively)
As far as using 3 point versus 1 point EF's, each have their own strong points.
Using 1 point EF's: Less overheal from the initial heal, the HoT, and the beacon transfer, as many small heals are easier to use than one large one. You are able to apply the HoT to more people, which means more people get the +30 second Illuminated Mastery renewal (since each HoT tick refreshes it). Less RNG on Divine Purpose (30 1-point EF's vs. 10 3-point EF's, as an example).
Using 3 point EF's: Fewer expended cooldowns. Able to store up Holy Power for emergencies (using 1 point EF's keeps you at 0 HP for most of the fight, except in predictable situations, but that's what Holy Avenger and other cooldowns are for if you choose this method).
Tada! If you had the time, yes, you should be using 1 point EF's as it's very mana efficient. However, it does take more time and puts a crimp in your throughput. Using 3 point EF's, you have more time to not only cast spells overall, but these additional spells could be things like Holy Radiance or Divine Light on Beacon for more HP which means more EF's over the course of the fight. It comes down to raid size, raid composition, your role in the raid, your playstyle, and your mana capacity as to which one would be better, and in truth it's more of a flavor thing than anything else. 3 point EF's means that you end up needing a bit more mana since you'll have more overheals, but you'll be more able to react to sudden damage. However, if you have other healers capable of handling that, such as priest with shielding, you can go the more efficient manner of 1 point EF's and turn the extra mana you're not spending into other secondary stats like Crit or even more Mastery.
Edited by Wards on 4/21/2013 5:30 AM PDT