I should say, right off, that there's a small rules gray area involved here, and the whole thing might yet fall apart. More on that at the end.
Also, it's possible, of course, that I'm getting excited over a conceptually sexy card that isn't actually that good on the table. Only playtesting will really show how good this card is.
Anyway, here's what I'm thinking: the intent of Transfusion (from the artwork) seems to be to move a pile of enchantments from one (dying) wolf to another (living) wolf. But that's not what it really is; it's a Block transmitter. It's a Nullify dispenser.
Since I mostly play a non-standard Beastmaster, lets imagine a really nonstandard control oriented Beastmaster. (This might work better with a Wizard in practice, but I'm brainstorming here, not building the tournament version yet).
The deck, at its core, is
Six
Enchantment Transfusion
Some Amount of
Nullify
Block
Reverse Magic
Reverse Attack
Retaliate
Mind Shield
Jinx
And for Support either
Enchanter's Ring
Fellella
Feral Bobcats
Pet Steelclaw
Or maybe
Enchanter's Ring
Arcane Ring
Moonglow Faerie
A 21 mana Angel or the Lord of Fire
And Why Not
Enchanter's Wardstone
Ok, here's how the book works:
The mage casts both Block and Enchantment Transfusion on himself, and hangs out within two zones of his creatures. Later, when his Steelclaw Grizzly (or whatever) is the target of a big attack, the mage reveals the Transfusion on himself, and uses it to move the Block over to the Griz, and just in time, the Block intervenes to save the Bear.
Or, if he has a little more mana, he sends over a Reverse Attack. Or a Retaliate. Or if the threat is Curses and Incantations, he sends over a Nullify or a Reverse Magic.
This technique prevents the defensive enchantments from being baited by scrub attacks by casting and storing them away from the action -- and only using them against targets that matter. The mage is now playing a MtG style counterspell deck, and choosing whether to say yes or no, instead of trying to say no to everything.
Now, obviously, this strategy has some weaknesses. Every time the mage wants to prepare a rescue Nullify, he needs to cast a Nullify and a Transfusion on himself or some other creature (Bobcat/Faerie). The Beastmaster's familiar, Fellella, is great here, because she's a free action (and some mana) every turn to cast a defensive spell. And you can stockpile these actions by casting multiple Blocks/Reflects/Transfusions ahead of time.
Alternately, the Wizard has two rings that can help bring down the mana cost of these spells, and the book cost is very low for a mage trained in Arcane.
Either Way, the actual mana cost is quite low with even just the enchanter's ring: 1 for the face down Transfusion, 1 for the face down defensive spell, 1 to use the Transfusion, and then whatever you'd normally pay to reveal the defense.
Aside from that, the other major weakness is that you can only put 6 Transfusions in a book, and you probably have to put in all 6. 6 is a lot if the Beastmaster or Wizard has other plans, too. But remember that the strategy isn't to Always Say No (you can do that more efficiently without using the Transfusions), it's to be able to see what the attack is before choosing to permit or deny.
And hey, maybe you don't even use the Transfusions every game, or you run out, or you just can't cast them for some other reason. Your blocks and nullifies are still some of the best cards available.
One last thing about that rules gray area I mentioned at the top.
It's not stated anywhere, and it's implied otherwise, but it's possible that defensive enchantments will only trigger if they're on the target before the attack.
The relevant part of Block's rules text is, "When this creature is attacked, you MUST reveal Block during the Avoid Attack Step. Block counts as a Defense and the attack is avoided." I read that as saying that I must reveal the block during any Step 2 the block could defend against. It is possible to read that another way, though; it might mean that Block actually triggers at step 1 "when this creature is attacked", but I don't do any revealing or countering until Step 2.
I think this would be inconsistent with other rulings where enchantments like Block are ignored completely until step 2, and are not treated as delayed triggers, just resolution steps, but I'm not the guy who makes the rules.