I have been watching some streams and sometimes, I read comments stating that Shaman should use their hero power to get a totem first. I search around and found some interesting facts about totems.
From
IHEARTHU.com's 30 Bizarre Hearthstone Rules:
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18. End of turn minion abilities activate in the order you summon them. For instance, if you play an Imp Master, and then create a Healing Totem that turn, the Imp Master will damage itself and then heal back to 5 HP. If you summon them in the reverse order, the Healing Totem will activate first, and you’ll only have a 4 HP Imp Master."
The above is a specific situation where you want to totem after the Imp Master.
"
22. Shaman’s hero power can only create a totem if none of that type are on the board. If you have 3 totems out, you will get the 4th totem you don’t have with 100% probability. If you have 4 totems out, you’ll get an error when you try to use your ability."
I didn't know about the above fact. More on that is elaborated in the
IGN's Shaman Guide:
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The Shaman can summon four different kinds of totems through his Hero Power. Each totem has an equal chance of being summoned and only one can be on the field of each kind at a time. Summoning a second totem will yield a 33.3% chance to summon a specific one; with a 50% chance to summon one of the remaining on the third summon in play. Attempting to summon a fifth totem will not result in another summon."
So in general, why should you hero power a totem first if you have the mana? I think the main reason is you want to try getting the Wrath of Air Totem to boost spell power before casting your damage spells for that turn. Secondly, like with card drawing, you want to do it first to re-assess the situation and see if you will play your cards out differently.
*New* Thirdly, you can use the fact of unique totems to get out totems that you want before sacrificing away one of it.
