[Grozmok]

AC>HP>WIS>STA

Compilation of Shaman STAMINA vs. WISDOM data points (Note: This does not take +HP items into account)

For each +1 to STA (below 255), a Shaman gains 0.05 hit points per level (so +2 hp per +1 STA at Level 40).
For each +1 to STA (above 255), a Shaman gains 0.025 hit points per level (so +1 hp per +1 STA at Level 40).
Given the HP-per-STA ratios +1 STA buys the Shaman an effective 0.025 (STA>255) to 0.05 (STA<255) HP per level

For each +1 to WIS (below 200), a Shaman gains 0.2 mana points per level (so +8 mana per +1 WIS at Level 40).
For each +1 to WIS (above 200), a Shaman gains ~0.0775 mana points per level (so +3.1 mana per +1 WIS at Level 40).
Given the Mana-per-WIS ratios +1 WIS buys the Shaman an effective ~0.08 (WIS>200) to 0.2 (WIS<200) Mana per level

A Shaman can convert their own HP to Mana using various Cannibalize spells; the theoretical best conversion ratio being 1.57 (Cannibalize III @ Level 60) hp:mana:

Cannibalize I (LVL 24): consume 50 hp, gain 19-30 mana (conversion ratio is 1.66 to 2.63 hp:mana)
Cannibalize II (LVL 38): consume 67 hp, gain 30-42 mana (conversion ratio is 1.60 to 2.23 hp:mana)
Cannibalize III (LVL 54): consume 100 hp, gain 39-47 Mana (conversion ratio is 2.13 to 2.56 hp:mana)
Cannibalize IV (LVL 58): consume 148 hp, gain 81-82 mana (conversion ratio is 1.80 to 1.83 hp:mana)

A Shaman can convert Mana to HP using various Healing spells; the theoretical best high-bandwidth hp:mana conversion ratio being 6.0 (Torpor):

Greater Healing (LVL 29): consume 115 mana, gain up to 350 hp (conversion ratio is 3.04 hp:mana)
Stoicism (LVL 44): consume 180 mana, gain 640 hp (conversion ratio is 3.56 hp:mana)
Superior Healing (LVL 51): consume 185 mana, gain 600 hp (conversion ratio is 3.24 hp:mana)
Chloroblast (LVL 55): consume 331 mana, gain up to 994-1044 hp (conversion ratio is 3.0 to 3.15 hp:mana)
Kragg's Mending (LVL 58): consume 400 mana, gain up to 1950 hp (conversion ratio is less than 4.875 hp:mana)
Torpor (LVL 60): consume 200 mana, gain 1200 hp (conversion ratio is 6.0 hp:mana)

plus you can probably leverage some additional slow-rate high-efficiency conversion with stuff like:

Regrowth (LVL 52): consume 180 mana, slowly gain up to 4100 hp (limited-bandwidth conv. ratio of 22.78)

General thoughts:
Given that Shamen can readily convert their HP to mana and back, their HP & mana pools both contribute to their overall "mana pool depth"
Given the HP:Mana conversion ratios we can generalize and say that 1 Mana Point > 1 Hit Point (in fact, 1 MP ~= 1.6 HP or worse).
Given our best-case sustainable HP-to-Mana conversion rate of 1.6:1, each +1 STA buys the Shaman an effective 0.016 (STA>255) to 0.031 (STA<255) Mana per level.

For WIS < 200 and STA < 255, each +1 WIS buys the Shaman over 6x as much Mana (0.2 vs. 0.031) as would a +1 STA
For WIS > 200 and STA > 255, each +1 WIS buys the Shaman over 3x as much Mana (0.08 vs. 0.025) as would a +1 STA
Even for WIS > 200 and STA < 255, each +1 WIS buys the Shaman over 1.6x as much Mana (0.08 vs. 0.05) as would a +1 STA

For pure Mana consideration, a higher WIS *dramatically* beats out over a higher STA


That said, there are some meta-considerations as well to be taken into account:
When you reach 0 mana, you are OOM. When you reach 0 HP, you are dead. Therefore, HP are obviously important.
The higher your HP, the bigger your "Cannibalize buffer" is, i.e. how much overhead you have to play with before feeling vulnerable.
Since it's "easy" to reach your stat caps, any +WIS above cap is wasted and should instead be giving you +STA (and vice-versa).
Draining your Mana pool is better than draining your HP, in that you regain Mana faster while medding than HP.
Draining your HP pool is better than draining your Mana, in that others (esp. Druid, Cleric) can refill your HP for you much more easily than your Mana.
None of this takes any special HP or mana regen items into account.

TLDR: AC>HP>WIS>STA