Ignore what Rawr says about it because its wrong. Its the BiS. You can edit the item yourself to reflect the trinket.

OOO Not sure how to do that, could you give me a quick run down?

Right click the trinket, Edit... ,under Base Stats, change the mana per 5 value to 144.

Alternatively you can base the RAWR edit on an existing trinket special effect which may (or may not) better model the stacking effect (I used the stacking effect of the Illustration trinket for example and altered the values and trigger accordingly).
For example I did the following:
Right click trinket (as stated) and choose Edit ...
(Note in my RAWR i get both the i245 and i258 so make sure to edit with the correct stats )
Under 'Special Effects' in the middle right side click 'Add' (or Edit if you already created one)
Under 'Base Stats' select the 'Mana per 5 sec' and type '18' into the field on the right which is currently '0'
In the bottom lists then change:
Trigger : HealingSpellCast
Duration : 10
Cooldown : 0
Chance 100.00 %
Stacks : 8
Click OK , and you should be done

Repeat for the i245 placing 16 in the mp5 field rather than 18 , hth

A while ago we had a short conversation about this bonus as I was trying to find a good use for it. At the time my idea was shot down because it was believed that if you judged two different mobs your judgment would only actually effect one of the mobs, however this is not true. I'm not sure if something changed or if people just never did any real testing on it and just went off what they "remembered" (I know I did), but as of two days ago judging two resulted in getting a proc off of both mobs when alternating between them. I did not test to see if this were true for anyone besides myself, so I'll have to make sure of that as well when I get on next.

I do not have the 2pc bonus so I cannot test it for 3 mobs, however I don't see any reason as to why it wouldn't work. In a scenario where you have more than 2 pallies this might not be totally useful, however I can definitely see it coming in handy, especially considering I often get misses which results in the debuff falling off. In light of all this, I wouldn't exactly discount it entirely just because it doesn't result in a clearly defined throughput/longevity increase.

One thing I noticed about the 2-piece bonus: it makes me judge a lot more often because I'm actively trying to keep light up during multi-mob fights. With the change to judgements in 3.2, they are considered melee and can proc a seal of wisdom mana gain of 1200 - 1400 mana. Last night on Jaraxxus 10 man hard mode, I was actively trying to keep Judgement of Light on the boss and on any/all adds that were up nearly 100%. Judging that much ended up being a HUGE mana return, as I topped healing for the fight and ended with 33k out of 34k mana.

The extra healing was nice on that fight too. When the portal/volcano spawned I immediately judged and shocked it for the extra damage, but since they both have an aoe damage aura having light on them while they get burned was a nice addition to healing. The MT would have sacred shield, my FoL heal over time, and JoL on Jaraxxus which gives a lot of wiggle room to heal the debuffed person or run out with legion flame.

Redacted due to inaccuracies.

This hasn't been true (universally as far as I know, but definitely for Protection spec) at least since 3.0.

When we were running Naxx-10, I used to alternate Judgements on the two adds that Kel'thuzad summons, so that both had the attack speed debuff from Judgements of the Just. It was very obvious that the Judgement effect was maintained as I would judge -> tab target and the previous judge debuff would be at ~50% duration remaining, and tick down normally.

If the fight is easily handled without DivSac...perhaps it begs the question; why bother min maxing the 8% crit anyway? I can't picture any encounter where I need maximum possible longevity, but don't feel DivSac would be helpful. Either intense healing pressure is present and pushes my mana (in which case, DivSac is great) or it's laxed healing and a long fight...in which case DP + SoW + Flash of Light saturation in my rotations will more than keep me up.

With haste on gear bringing alot of us close to or over the FoL/GCD haste cap, something I have seen a couple pallies with high haste do is start removing points from Judgements of the Pure to put in other talents. For example, if you can get 98 haste over the soft haste cap, then you can go 4/5 JoTP instead of 5/5 and put the extra point in one of the holy utility talents (Aura Mastery/Improved BoW/Improved LoH/Improved Conc Aura/Blessed Hands), or put the point in Benediction/Divinity if you don't have those maxed out.

Any thoughts on whether doing this is viable, or whether you're better off stacking crit/mp5 past the haste cap or just letting your haste continue to go over the soft cap to reduce HL cast time further?

Healing with Holy Light haste is our biggest HPS increase until you reach 1968 haste rating. I'd see no reason to ever drop points from JotP.