I don't find this in any of our spell effects: Word of Glory has lost the old Last Word effect? So no more increased crit chance on low health targets?

Regardless, I'd still rather spend Holy Power on a spot heal instead of mana on a Flash of Light.

First thing I tried to do with Sacred Shield was macro it to another button, since we'd want it to be up all the time, but I'm not having any luck getting it to work, even in macros that work fine with, say, Divine Protection instead. If you've gotten Sacred Shield to work fine in a macro can you post it? Humble apologies if I'm missing something obvious.

It's on the GCD and thus can't be macroed to another ability on the GCD.

There are a few things to consider in the debate of Eternal Flame and Sacred Shield.
First of all is the number of ticks in relation to haste. Currently at level 85 you gain a 13th tick at 24.97% haste, which most of us will be at with the 5% Spell Haste buff.
Realistically you wouldn't want to math it out with doing 10 ticks, as for the majority of raiders it would not be doing 10 ticks. You gain 11 ticks just by having Seal of Insight on.

The second is that you also have to compare the Eternal Flame with using both Sacred Shield and Light of Dawn. Just doing Word of Glory is not good enough. In Dragon Soul we have quite a lot of AoE damage and could be more beneficial to have spent that 3 Holy Power on a LoD whilst also being able to SS somebody.

Finally depending on how often X takes damage, there is a chance of the HoT tick being wasted. It is quite possible for them to be on 100% health when it ticks. With SS however you have a 6 second window where any damage taken during it will count towards the absorb. Putting it on the tank you can pretty safely bet none of it will get wasted.

Apologies, the 13 ticks was for EF. SS does scale with haste yes, but nowhere near as well. Whilst 25% Haste may give EF 13 ticks, it won't give SS any additional. I will do the math for SS ticks at some point, but I would expect us to not gain any extra ticks unless under extreme circumstances.

I did the math based on Binkenstein's break points spreadsheet, which he's put away for now. The resulting set of cards, however, are found here: Maths of Pandaria: Healer Haste Breakpoint Cards - Blogs - Totem Spot. The images there should update in a couple days after he's added Sacred Shield to the Paladin list. It does scale horribly. The first extra tick is at 10% Haste but every additional tick requires an additional 20% Haste. (30%, 50%, 70%, etc) Eternal Flame is roughly every 10% with the first extra tick around 5% Haste.

On the topic of SS, I randomly just found out that it does indeed "roll" its duration, much like Inquisition, Curse of Agony, Rejuv, etc.