I wrote before about Mana Tide Totem and how it seems like a large and meaningful anomaly in the current mana regen landscape.
Patch 4.0.6 significantly changed Mana Tide by basing the bonus off the Shaman's spirit rather than the recipient's spirit. I understand this was to prevent Mana Tide from being overpowered when used with temporary spirit buffs like Core of Ripeness. Preventing temporary spirit buffs from generating more than three times as much mana as they were intended to is probably a good thing.
Elevating the value of Spirit to obscene levels for Shamans was not.
If you are a Discipline Priest in 359 gear, gaining 100 spirit would give you about 5k more mana to spend over a 6 minute fight. For a Paladin its slightly less, only around 4.6k mana. Druids get 4.8k. Holy Priests, thanks to Holy Concentration get a whopping 6.5k. What about Shamans?
Ignoring Mana Tide, Shamans get around 4.6k just like Paladins. Mana Tide essentially multiples that extra 100 spirit by five for 16.8 seconds out of every 180 seconds, or 9.33% of the time. That's the equivalent of a 37.3% increase to your spirit. If spirit was increasing your mana by 4.6k without Mana Tide then it will be increasing it by 6.4k with Mana Tide.
No big deal, around the same as the Holy Priest. Except for the fact that the other people in your raid get the same bonus. If you are in a 10-player raid, your 100 spirit generates not only an additional 1.8k mana for you, but also for the two other healers. So the total healer mana from your 100 spirit is 9k. That's if the other two healers are also paladins or shamans. If one is a holy priest and the other is a druid then your 100 spirit generates 11k extra healer mana for your raid.
If you are in a 25-player raid with 2 paladins, 2 holy priests, 1 discipline priest and 1 druid, then your 100 spirit generates 19.1k mana.
So in 10 player raids a shaman might get around 1.7 to 2.4 times the benefit from spirit that another healer would get. In 25 player raiders, the number is more like 3 to 4 times the benefit in terms of total mana restored to the raid. Of course shaman are also widely thought to be one of the weaker healers in terms of throughput. That means that giving other people mana is probably better than giving yourself mana.
If other healers stack spirit as high as they can, reforging other stats to it and matching blue sockets with int/spirit gems, then shaman should be taking this a step further. Gem pure spirit, use spirit enchants in every slot (such as 40 spirit to chest rather than 20 stats), eat spirit food and drink a spirit flask. Tell your other raid members they can let a little bit of their spirit go in favour of throughput because you are the mana guy and they don't have to worry about it.
It may not be possible to directly compare throughput to mana stats, but when a mana stat that is desirable to other healers is four times as good for you as it is for them, there is no possible way that at throughput stat can keep up.
And still there is the problem that there is no analog to Mana Tide anywhere. More resto shamans means more mana for your raid. Less shamans means less. You cannot substitute anything, and you can stack as many as you want.