For the discussion about who you should give the fragments to, I think it should be to the one that comes to raids the most while still fairly balanced with the one who also heals very well.
In my guild of friends, size of 5 raiders, we PuG Ulduar 25 and have gone to tier bosses fairly easily. We reserved the fragments to me, the pally healer. To those of you that say pally healers can’t aoe heal efficiently, you’re wrong. In most fights like XT and Ignis I beacon tank and aoe heal more than coh priests and resto druids given that we don’t have more than 6 healers that reduce my effective healing.
There’s one thing I’m confused about the proc. Is the shield done by 15% of the effective healing or 15% of raw heal you do?

Thingie procs, you have 15 seconds to heal as much as possible (to gain the most from the shield)…

Use that “next spell crits”, lay on hands, Holy shock, Holy Lightspam until 15 secs have passed (with the random holy shock in the middle)

Wouldn’t that boost the shield majorly?

IMHO, druids would not be a bad choice. if you consider that druids have a very high HPS on a main tank due to HoT’s constantly rolling, plus the fact that they will be forced to let lifebloom “Bloom” in 3.1, plus the huge buff to nourish in the upcoming patch… seems to me like the proc will fit in very nicely. i’m not saying druids are the best choice, just that they certainly wont be a bad choice at all.

with all the AoE that bosses in Ulduar and beyond any healer that has good skill and very high raid attendance (and low flight risk) would be just as good with this mace as any other healer. you will need lots of raid healing and a shammy with the mace would be a great choice (assuming that all the chain targets would get the shield and not the primary target). same goes for Holy priests.

To take that one step further, have the second highest get the shards when top roller isn’t available.

Consider, my spriest will never hit the dps numbers of an arcane mage. A discipline priest won’t ever hit the raw heal numbers of a paladin or druid main tank healing, throughput.

These factors are, if you are distributing the mace based on the proc solely for main tank healing, important to remember.

Sure, a discipline priest has the targeted prayer of healing coming up, but that applies to holy priests too. And, if one discounts shamans based on chain heal spam on tanks, one can’t go and use that argument to argue for targeted prayer of healing spells, as chain heal is a smart heal etc.

With upcoming changes to mana regen for holy priests, it seems to me they are simply not the best choice for a main tank healer, plus the tools that other classes have make it easier for them.

But of course you have to know your healing team, you have to know what assignments are typical, you have to know all this and judge based on your raiding team who you would most like to see have this legendary.

Healing isn’t capped, having or not having this mace won’t make or break a raid, it’s a status icon.

One of the key points I tried to make in my initial post is that while the proc is a fantastic proc, ultimately its up to the recipient of the mace to use it. Originally I think I would have said “Pally mace”, but after thinking about it I really think its up to the user.

Regarding the proc, based on what information is available on datamine its a flat 10% proc with no cooldown. http://ptr.wowhead.com/?spell=64415 (shows the proc rate) http://ptr.wowhead.com/?spell=64411 (shows the buff after proc, and Cooldown: n/a).

But I guess my main point is that the throughput is really based on the skill of the user. All healing classes have abilities to push out additional benefit from the proc through certain abilities… I really feel that this really is a Bring the Player not the Class situation.