Tamiyo, Field Researcher is an interesting card, because it’s a lot less self-sufficient than other planeswalkers. Normally, you can jam a planeswalker onto an empty board and it’ll be excellent, but with Tamiyo this is not the case. For most planeswalkers, it’s enough that they have nothing, but Tamiyo cares more about what you have than about what they have.
Luckily for her, there are multiple decks in this Standard format that are very good at having something in play, and they all happen to be some combination of Bant. Let’s analyze her abilities:
+1: Choose up to two target creatures. Until your next turn, whenever either of those creatures deals combat damage, you draw a card.
Tamiyo’s base ability. If this is good in your deck, then Tamiyo is good in your deck. If it’s not, then you probably want to look somewhere else. If you can play Tamiyo, +1 it, and immediately draw 2 cards, then you’re way ahead—4-mana cards that draw 3 have been good before, and having a Tamiyo in play with 5 loyalty counters is worth much, much more than an extra card in hand. If Tamiyo survives (and at 5 it’s not easy to kill), you can then draw an extra 2 cards, and at this point it becomes very hard to lose the game. To really get as much as possible from Tamiyo, you want to have played a creature on turns 2 and 3.
There are two important things to note with Tamiyo’s +1. The first one is that it specifies combat damage, but not to what—you can attack a player, a planeswalker, or deal damage to creatures—you’ll draw the cards no matter what. This makes it so that the only way to stop you from drawing something is to either prevent the damage somehow or kill the creature. It also doesn’t limit the amount of times you draw cards—if you have a creature with double strike, for example, you’ll draw 2, and if it has vigilance, then you can draw when it attacks and when it blocks. In theory, you could target 2 creatures with vigilance and double strike and draw 8 cards off a single Tamiyo activation. It also happens to be a great combo with Blessed Alliance, since you can untap your 2 attackers, block, and draw another 2 cards.
The second important thing is that you can target any creature, not just yours. If you both have Sylvan Advocate in play, for example, you can target both and then your opponent will very likely not block. On their turn, even if they kill your Advocate so that they can attack, you’ll be drawing an extra card at the cost of 2 loyalty. You can still get beaten by instant-speed threats such as Archangel Avacyn or Collected Company, but, in the absence of those, the “bad case scenario” for Tamiyo isn’t even that bad, as you get to gain 5 life and draw two cards or gain 6 life and draw 3-4.
-2: Tap up to two target nonland permanents. They don’t untap during their controller’s next untap step.
This is an ability that can be used aggressively or defensively, but it’s much better on the offense because you get 2 uses out of it (it only stops 1 attack from whatever it targets, but stops 2 blocks). I imagine that most of the time you use Tamiyo, Field Researcher’s -2 twice in a row, you’re going to kill your opponent since you get rid of 2 blockers, then 4 blockers, then 2 blockers. This ability works well with the +1, because it locks the blockers for a turn, which lets you swing with your creatures past them to draw more cards. This ability also makes extra copies of Tamiyo non-redundant. Imagine, for example, that both players have 2 creatures in play. I play Tamiyo, -2 it, and hit my opponent. Then the following turn I -2 it again, play a second Tamiyo, +1 it, attack and draw 2. Next turn they will still be tapped and I can draw 2 more cards and have a Tamiyo on 6, or I can lock them for another 2 turns and still have a Tamiyo on 1.
It’s important to realize that Tamiyo can tap any nonland permanent and not just creatures—it can often be right to tap mana artifacts, for example, and you can also tap Gideon to make sure he can’t kill Tamiyo.
-7: Draw three cards. You get an emblem with “You may cast nonland cards from your hand without paying their mana costs.”
The old Ancestral Recall + Omniscience package. While it’s not guaranteed to win you the game, it can get you pretty close, and I’d say that Tamiyo is probably the best planeswalker when you have Doubling Season in play, along with Jace, Architect of Thought. In Standard, it’s best paired with creatures with activated abilities, of which conveniently there are plenty in Bant. Cards like Duskwatch Recruiter and Eldrazi Displacer, for example, offer great uses for your mana once you can stop paying for spells, and Tamiyo also happens to let you cast whatever you Duskwatch into for free.
This combination of abilities makes Bant Company the perfect deck for Tamiyo—it has plenty of creatures to draw cards from, has creatures with vigilance and high toughness, has enough of an aggressive component that you can use -2 to threaten lethal, and has enough expensive cards + activated abilities to make it very likely you’re going to win the game if you ever ultimate. Tamiyo is a card that does almost nothing if you’re behind, but one that wins you the game if you’re slightly ahead, and Bant has the mechanisms to make sure it’s slightly ahead when you drop it (as do GW Tokens and Bant Humans, which are other possible homes for the card). There is some tension with Collected Company, of course, but I think you can very easily play 2 Tamiyos without hurting your chances too much.
This deck can also run 4 of my favorite card in the set, Spell Queller. Other than that it’s a pretty standard Bant list, but I’ve tweaked it a small amount to add a couple of 2-drops that can work with Tamiyo (the Den Protector and the fourth Duskwatch Recruiter), as I really want to curve creature + creature into her.