I think a Malefic deamon summoning army sounds good at first but I’m not sold on it. Even the battle report that Reece Robbins posted he lost to a mediocre Space Marine army. Also if you don’t play with or against deamons normally it might shock you how bad their troops are as they evaporate off the table. Tzeentch horrors do damage via psychic powers and the only good one is the warp charge 3 power. So the first two turns you are only summoning and not damaging your enemy. Also you will still need divination to get the 4++ plus Grim to make a safe bunker for your heralds. So the only power you need to try and deny the witch will be the 4++ from divination to avoid the 2++ re-rollable bunker.
Dice needed to get near the 90% that was close to passing a LD 10 test for the old psychic test is as follows.
I’m giving my vote to Sanctic as it has a lot of great powers in a army that will have a large amount of warp charges. Plus the combos that you can do now are just crazy 2++ storm shield termies with two priests so you can re-roll your armor save in close combat. I can see another era of Grey Knights ruling the tables with one to two extra detachments to get some of the tools they don’t have.
In a completely different direction some psychic focused armies like Thousand Sons theme CSM lists got worse. Needing 3d6 to cast a crappy witch fire power at near 90% is rough as you still need to roll to hit with them.
The Take Away!
This is my take away from the new psychic phase is this after a handful different reviews from groups that I consider reliable and my own opinions.
WFB does it better! The 40k psychic powers are not scaled well in proportion to what they can do vs. how much they cost vs. how easy or hard they are to deny.
So in the end it is a great idea but poorly executed as normal for GW dealing with 40k. The system could have been great if they retooled all the current powers from all the codexs creating casting values into a more robust and thought out system.
PS: Abhor the Witch. Destroy the Witch. I play Black Templars!
Jaded Gamercast 
Malilific cause summon a bigger dick!
I think a Malefic deamon summoning army sounds good at first but I’m not sold on it. Even the battle report that Reece Robbins posted he lost to a mediocre Space Marine army. Also if you don’t play with or against deamons normally it might shock you how bad their troops are as they evaporate off the table. Tzeentch horrors do damage via psychic powers and the only good one is the warp charge 3 power. So the first two turns you are only summoning and not damaging your enemy. Also you will still need divination to get the 4++ plus Grim to make a safe bunker for your heralds. So the only power you need to try and deny the witch will be the 4++ from divination to avoid the 2++ re-rollable bunker.
Dice needed to get near the 90% that was close to passing a LD 10 test for the old psychic test is as follows.
Warp Charge 1 3d6
Warp Charge 2 6d6
Warp Charge 3 9d6
Or number of Warp Charges required x 3
I’m giving my vote to Sanctic as it has a lot of great powers in a army that will have a large amount of warp charges. Plus the combos that you can do now are just crazy 2++ storm shield termies with two priests so you can re-roll your armor save in close combat. I can see another era of Grey Knights ruling the tables with one to two extra detachments to get some of the tools they don’t have.
In a completely different direction some psychic focused armies like Thousand Sons theme CSM lists got worse. Needing 3d6 to cast a crappy witch fire power at near 90% is rough as you still need to roll to hit with them.
The Take Away!
This is my take away from the new psychic phase is this after a handful different reviews from groups that I consider reliable and my own opinions.
WFB does it better! The 40k psychic powers are not scaled well in proportion to what they can do vs. how much they cost vs. how easy or hard they are to deny.
So in the end it is a great idea but poorly executed as normal for GW dealing with 40k. The system could have been great if they retooled all the current powers from all the codexs creating casting values into a more robust and thought out system.
PS: Abhor the Witch. Destroy the Witch. I play Black Templars!