A number of shamans (including Philondra and Grayshock in this thread) noticed that less mana is granted from Improved Water Shield procs than from Water Shield orbs triggered the "normal" way (i.e. by mob damage and environmental factors.) We speculated as to what the mechanic might be, but had no hard data to validate our assumptions. I decided to gather some data to see if we could figure out what the issue was. Please check to see if my calculations and conclusions are accurate.

Abbreviations:
2T7 = the two piece tier 7 set bonus, which increases the strength of Water Shield by 10%
IS = Improved Shields
IWS = Improved Water Shield
GoWM = Glyph of Water Mastery

Methodology:
1.) I started with a standard 0/14/54 + 3 spec with 0/3 IS. I removed all T7 gear and water-shield related glyphs, and went to Crystalsong Forest.
2.) I went to Crystalsong Forest and activated WS.
3.) I attacked a mob and recorded the mana return from each WS orb.
4.) I refreshed WS until I had 50 orbs had triggered, then killed the mob.
5.) Once out of combat, I cast LHW until I recorded 50 crits (refreshing WS as necessary) and recorded the mana return from 50 IWS procs.
6.) I then equipped 2T7 and repeated steps 2-5.
7.) I returned to the Lexicon of Power in Dalaran, added GoWM, removed 2T7, went back to Crystalsong Forest, and repeated steps 2-6.
8.) One I had tested the returns for all permutations of 2T7 and GoWM with 0 points in IS, I added 1 point in improved shields, removed GoWM, and repeated testing as above. I did the same for 2/3 and 3/3 improved shields.

Notes:
1.) As anticipated, GoWM had no effect on mana granted from Water Shield Orbs. As such, data points for tests without GoWM are omitted.
2.) Data listed below for mana returns are averages rounded to the nearest integer. In no case was the variation between procs greater than +/- 1 mana.
3.) In "Test Condition" below, the percentage in parentheses represents the expected gain in mana granted by water shield orbs according to the combination of IS points and the presence or absence of 2T7.

From the data above, we see the following trends:
* The difference in mana granted between a baseline (0/3 IS, no 2T7) WS proc and a baseline IWS proc is 50 mana, or 50% of the passive mp5 granted by a baseline WS.
* Both IS and 2T7 increase the amount of mana granted by both WS and IWS.
* Although the absolute difference between the two increases, the percentage difference remains the same, and is in line with what we predicted should happen given the wording of the IS talent and the 2T7 bonus.

Conclusions:
* For a max rank Water Shield, standard WS procs grant B*(O+P) mana, where B is the total percent bonus to each orb granted by talents and bonuses that improve the per-orb mana return of WS (namely IS and 2T7), O is the tooltip mana per orb for a naked, 0/0/0 spec shaman, and P is 50% of the base passive mp5 of an unglyphed water shield.
* IWS procs, in comparison, only gain mana equal to (B*O); they do not gain any bonus, scaling or otherwise, from the passive mp5 of water shield (P).
* In other words, WS procs gain a baseline modifier to mana return (that happens to scale with IS and 2T7), but IWS procs do not. It is unclear why this discrepancy exists.

The above conclusions are counter intuitive for two reasons:
1.) A logical reader of the tooltip would come to the conclusion that IWS and WS procs should return the same amount of mana. This is clearly not the case as of patch 3.0.3.
2.) The bonus modifier P, which is calculated from the passive mp5 of water shield, is unaffected by abilities that increase only the passive mp5 (GoWS), but *is* affected by abilities that increase only the WS orb procs (Improved Shields) and abilities that affect both (2T7).

Interesting! Thank you so much for conducting this test. Your table and method were very easy to understand too.

Before wrath came out, I was unsure about the benefits of IWS, but I really like it now and have itemized for crit because of it. Even with the discrepancy, IWS is win.

That being said, this is probably a bug, yes? Has anyone seen blue posts regarding the discrepancy? If it gets fixed in an upcoming patch, that means IWS will be even more OP. Exciting!

I believe this is a bug with Rank 9 of Water Shield. I'm still using Rank 8 and have the exact same procs from combat and heals. (246-247 in my case.)

I'm using Water Mastery, Imp Shields, and IWS and therefore have all the factors except 2T7 in play. Perhaps you could check a Rank 8 as max level and see if you have the same results.

Before I posted I went and checked all ranks of WS available to me at 75, and found that all ranks except Rank 2 are proccing the same from combat and IWS. Rank 2 actually procs more from IWS than combat. (93 IWS, 84 damage).

what about with the water shield totem?

Our best guess is that the non-IWS orbs of max rank water shield (only) grant an extra 50 mp5 when the orb is triggered by damage, and this bonus is affected by all percent-based modifiers that affect WS orb mana gain. Without seeing exactly how the ability is coded we can only guess whether it is a static 50mp5 or if it is 50% of the base passive mp5. I presumed it was 50% of the passive mp5 because that number makes more sense than (or, depending on your point of view, isn't quite as random as) a static 50 mp5. However, I cannot unlearn max rank WS, and the downranking changes make it impossible to determine if my results are because of some strange interaction between downranking and WS without levelling up another character.

Questions I cannot answer because I'm not going to level another character just to test this (If you have a low-mid level shaman and want to test this out, feel free to provide us data):

* Does the bonus only apply to max rank Water Shield?
* Does the bonus only apply to Water Shield 9? (this is a different question than the one above)

Questions we cannot answer without Blizzard confirmation:

* Is this difference intended?
* If not, which is giving the proper amount? (Hint: It probably won't be the one we're hoping for)

Questions to be answered/discussed (I'll try to get some testing done this weekend):
* How does Totem of the Thunderhead interact with our data? Could this totem be viable for a crit healing build, particularly before the PvP LHW totem comes out?

A minor point, but S5 is supposed to start Dec 17, and presumably the totem would be available after that point if you control wintergrasp.

I tested all ranks of Water Shield (via the spellbook) and Rank 1, 3, 4, 5, 6, 7, and 8 all react the same from IWS and damage. Rank 2 returns more mana from IWS than damage, and Rank 9 returns less mana from IWS than damage.

It has nothing to do with whatever rank your max is, it is a bug with Rank 9.

As of 3 days ago on the PTR:

You have a 33/66/100% chance to instantly consume a Water Shield Orb when you gain a critical effect from your Healing Wave or Riptide spells, and a 19.8/39.6/60% chance when you gain a critical effect from your Lesser Healing Wave spell.

Handyhoof listed the proc percentages, but I have been unable to confirm anything related to WS9, as I have been unable to access the PTR due to the account-flagging issue various people are reporting.

I can also report that although I was unable to get Totem of the Thunderhead after 16 Underbog runs, one of my fellow guild members did -- and he reported that Improved Shield and 2T7 *were* affecting the mana granted from the totem, giving us a maximum of 569 mana from IWS or 631(!) mana from normal triggering.

In other words, with 5/5 Tidal Focus, 3/3 Imp Shields, 2T7 and Totem of the Thunderhead, one normal WS proc will actually give you enough mana to cast one LHW with 5 mana to spare.

According to my spreadsheet (see the crit healing thread for more details), LHW at....

2400 SP
35% crit (including all talents, gear, and buffs)
500 haste rating
2pc T7
Ancestral Awakening
Tidal Waves
Tidal Focus
535 mana returned per IWS proc

Please note: no totem, no glyph

And for what it's worth, the spread sheet I have sees no appreciable difference in HPM with Totem of the Thunderhead. It's less than 0.1 difference for almost any play style. On the other hand, Deadly Totem of the Third Wind supplies 0.4 HPM for CH>LHW*2 rotation, and 0.7 for straight LHW spam.

As you mentioned in the bug report thread, I'm pretty sure our data conclusively shows that the problem is NOT with the improved shields talent, as many people assume and I had initially postulated myself, but rather with some sort of invisble modifier being applied to WS9. Hopefully Blizzard can make the WS and IWS mana returns match up so that this issue can be laid to rest.