i think she makes a fun intruder alarm idea. For the purpose of the deck people want her in though, the 4 color saheeli evolution list is just better and can come down on turn 2.
The thing with Saheeli Evolution is that its combo is slow and inconsistent in comparison. You need to get a 4-of and an 8-of (and 4 of the 8-ofs need a second card in order to work) into your hand if you want to win with the combo. And the 8-ofs all cost 3 mana or more. Vannifar can turn a 1-cmc creature into an entire infinite combo, and she can also do that with a 2-drop and a 3-drop, or a specific 2-drop, etc. She turns most board states, especially early board states, into one-turn kills. And she does that without casting any spells on the combo turn (which lets you ignore Spell Queller more often).
Combine that with the typical Turn 3 Saheeli kill needing a mana dork to work, and all Turn 2 kills needing a mana dork and too many specific other creatures to work (e.g. both Lotus Cobra and Renegade Rallier), and Saheeli Evolution doesn't gain enough speed points compared to Vannifar.
It's possible that combining both Saheeli Evolution and the Vannifar shell may produce the best deck, though. Both shells are mana dork-hungry, and it's easy to incorporate Felidar Guardian into Vannifar combo chains. Even better, Saheeli Rai can give Vannifar Haste (at a terrible price, yes, but the chance you juke out your opponent who tapped out for Goyf on Turn 2 on the draw just went up).
It's a nice feeling when a Pod-like deck can finally have an even match-up against Gx Tron in Game 1.
It's quite possible that Wizards dropped the ball the other way with Prime Speaker Vannifar - assuming she survives long enough, she can turn a mere 1-drop into a creature-based combo in one turn. With enough deck-warping and other resources, she can also turn singleton 2-5-drops and even a fetchland for Dryad Arbor into the same win. While she's more expensive, more restrictive colours-wise, and slower than Birthing Pod, she's more powerful.
I've been having reasonable success with a 4-Vannifar deck, loads of creatures, plenty of "Pod" chains leading to Deceiver Exarch + Kiki-Jiki, Mirror Breaker, and a relatively minimal creature toolkit. The deck is very capable of comboing off on Turn 4, and my current build can even combo off on Turn 3 (awww thanks, Torch Courier).
However, from my further testing, it's quite possible that a build that loads up on Vannifar, Saheeli Rai, and Felidar Guardian may end up becoming the best Vannifar deck. Saheeli Rai can effectively grant a fresh Vannifar Haste (at the grave cost of losing Vannifar after that turn), Felidar Guardian is part of the "Pod" chain leading to Exarch & Kiki-Jiki, and both plans love 1-cmc mana dorks so they can go off on Turn 3 more often.
Vannifar herself may never be better positioned: this Modern meta has an unprecedentedly high number of decks with only burn spells and Collective Brutality as maindeck removal (Arclight Phoenix decks, Burn, maybe BR Hollow One except the latest builds have 2 Fatal Push each, arguably UR Storm). Thus, Vannifar gets to survive a turn against surprisingly many decks (unless they bust 2 burn spells on her).
The thing with Saheeli Evolution is that its combo is slow and inconsistent in comparison. You need to get a 4-of and an 8-of (and 4 of the 8-ofs need a second card in order to work) into your hand if you want to win with the combo. And the 8-ofs all cost 3 mana or more. Vannifar can turn a 1-cmc creature into an entire infinite combo, and she can also do that with a 2-drop and a 3-drop, or a specific 2-drop, etc. She turns most board states, especially early board states, into one-turn kills. And she does that without casting any spells on the combo turn (which lets you ignore Spell Queller more often).
Combine that with the typical Turn 3 Saheeli kill needing a mana dork to work, and all Turn 2 kills needing a mana dork and too many specific other creatures to work (e.g. both Lotus Cobra and Renegade Rallier), and Saheeli Evolution doesn't gain enough speed points compared to Vannifar.
It's possible that combining both Saheeli Evolution and the Vannifar shell may produce the best deck, though. Both shells are mana dork-hungry, and it's easy to incorporate Felidar Guardian into Vannifar combo chains. Even better, Saheeli Rai can give Vannifar Haste (at a terrible price, yes, but the chance you juke out your opponent who tapped out for Goyf on Turn 2 on the draw just went up).
It's a nice feeling when a Pod-like deck can finally have an even match-up against Gx Tron in Game 1.
I've been having reasonable success with a 4-Vannifar deck, loads of creatures, plenty of "Pod" chains leading to Deceiver Exarch + Kiki-Jiki, Mirror Breaker, and a relatively minimal creature toolkit. The deck is very capable of comboing off on Turn 4, and my current build can even combo off on Turn 3 (awww thanks, Torch Courier).
However, from my further testing, it's quite possible that a build that loads up on Vannifar, Saheeli Rai, and Felidar Guardian may end up becoming the best Vannifar deck. Saheeli Rai can effectively grant a fresh Vannifar Haste (at the grave cost of losing Vannifar after that turn), Felidar Guardian is part of the "Pod" chain leading to Exarch & Kiki-Jiki, and both plans love 1-cmc mana dorks so they can go off on Turn 3 more often.
Vannifar herself may never be better positioned: this Modern meta has an unprecedentedly high number of decks with only burn spells and Collective Brutality as maindeck removal (Arclight Phoenix decks, Burn, maybe BR Hollow One except the latest builds have 2 Fatal Push each, arguably UR Storm). Thus, Vannifar gets to survive a turn against surprisingly many decks (unless they bust 2 burn spells on her).