Here is my assessment of the various Griselbrand based Reanimator decks. These decks weight the different functions of the Demon uniquely, which should help guide the rest of your deck building to be focused and always with a clear plan forward.
- Tinfins sees "Pay 7 life: Draw 7 cards" and goes nuts from there. The creature part is just a requirement for the supporting cards. If it was an Enchantment, they'd just be using Academy Rector. It makes no difference to them. They've specialized at using the draw engine to win them the game, the combat step can be at times just a convenient way to lower the storm count needed. They're combo with a big ol' capitol C.
- BR Reanimator sees a 7/7 Flying Lifelink the can cheat into play, the sooner the better. The draw 7 isn't really a crucial component, helpful in restocking for a second go around in the face of a Swords to Plowshares, but on the same terms as being a creature is to Tinfins. In a world where fast wins, they'll be the best, but their answers are all Sorceries, so their "draw 7 in response" options are lacking.
- BU Reanimator (hate this name, we're REANIMATOR god damn it) sees all parts of the card. Our win condition is through the combat step, but we have Force of Will to draw into, so there is a persistent potential use for the draw 7. We can draw up to reload in the same case as BR Reanimator, but we also have responses come our opponent's turn.
This logic makes me apprehensive of the casual dismissal of Force of Will in a blue Reanimator build. Sure BR has demonstrated it isn't required to win, but they're minmaxing with stuff like Simian Spirit Guide into Faithless Looting to ensure they're the best at what they're doing. If we're looking at Brainstorm and especially Ponder, we're saying that we're not trying our hardest at that T1 kill, and if so, then what are we doing? If the argument is for an extra strong T2 kill, then our best cards for this are stuff like Force of Will.