For Reference the tweet was
Holy Paladin T14 4pc bonus feels mandatory because its better than T15 heroic items :( please do something
"Still skeptical of this. Giving up all of those stats on the higher ilevel is a big cost."
To begin I will show exactly what stats you gain and lose by using T14 and T15. For the purpose of arguement I will assume Heroic Tier 2/2 upgraded on both sides. For the T14 set I will include Dark Animus Legs, and for T15 Lei Shen chest.
Here is a Pastebin from the notes I took, included are the stats and wowhead links. http://pastebin.com/katPizDc
If need be I can just copy paste the stuff here, but that is rather boring and will take up alot of space in this post. So here are the cliff notes.
Stamina Loss 6,020
Intellect Lost 1148
Spirit Lost 1633
Mastery Lost 361
Haste Lost 920
Crit Gained 409
That is the stat exchange, Comparing T15 heroic 2/2 Upgraded to T14.
The Stamina Loss is really the biggest loss here.
Now onto the important part.
What is it that makes our T14 set bonus so attractive? Well it is rather simple, Holy Shock is one of our most efficient and powerful tools. Procing IoL, Generating Holy Power and doing alot of healing for a cheap cost while being instant. Our T14 set bonus increases our useage of this spell by 33%. Meaning We Generate an additonal 33% Holy Power, Infusion Of Light and Raw Healing from Holy Shock.
Our T15 Bonus in Comparison Increases the healing done by Beacon of Light by 20%. This sounds somewhat attractive with the exception of on spells that make up a large portion of our healing.
The +20% is added off of the transferred amount, so on a spell like Eternal Flame, it would be a 10% increase in overall transfer amount. (Suppose a 100k EF hit, the transfer would be 60k.) Holy Light transfers at 100% and is a 20% increase. The problem lies with spells such as Holy Prism, Light's Hammer and Light of Dawn that transfer at 15%.
Suppose I cast a Light of Dawn that hits for 200k. The amount transferred would be 30,000 with the T15 set bonus an additonal 6,000 would transfer. Increasing the transfer amount by 3%.
Beacon of Light makes up a very small amount of Paladin healing in general, wheras Holy Shock and EF/LoD make up a large percent. The Additonal Infusion of Light proc's although relatively minor also increase our Holy Radiance/Holy Light Healing.
To show the difference in T14/T15 just based on raw set bonuses, I will do a log analysis of a durumu log by Kmy of Accidentally.
The first Log I will link is of a Durumu The Forgotten Kill.
The first thing I will look at here is Kmy's Holy Shock Healing.
Kmy Did 5,791,504 healing with Holy Shock having 30% Overheal.
Suppose Kmy Did not have the T14 set bonus this would be reduced by 33% meaning a net loss of 1,887,436 million Healing. There is also Beacon transfers on this of course. Looking at Kmy's beacon had 55% overheal. Meaning Kmy would Lose an additonal 424,673 beacon transfers.
Lost Healing total from Holy Shock = 2,312,109
But more importantly is the Eternal Flame/ Light of Dawn healing lost. Kmy cast 119 Holy Shocks during the encounter, assuming the same Holy Shock Useage but on a 6s Cooldown, a loss of 40 Holy Shocks or 40 Holy Power would have occured.
Kmy then did an additonal 16,694,626 healing with Eternal flame having a total of 97 Eternal Flames were cast. meaning an average of 172,109 healing was done per Eternal Flame cast.
Now the question is, how to figure out how much healing was lost with that 40 Holy Power net loss. Well, since I am close to the post cap in this post I will continue after this!